I personally don't see the appeal of Facebook pages. The only function I can see of "liking" any of these pages is to give Facebook more information so they can try to sell you more stuff.
In other words, it's a very poor trust network, because no one is using it that way. Most people 'like' a lot of stuff in a casual or even joking manner.
Unlike, recommend, and complain might be useful, but Facebook is an advertising platform, not a recommendation engine. I doubt they'll make that transition, because it would cut in on their revenue to let people clearly mark advertisers as unwanted.
The appeal to users could be social ("What brands do I associate myself with?") or promotion-related ("Become our 1,000,000th fan and get this free thing!", "Facebook-exclusive discount!"). Also I don't think Facebook lets you put in bio information (favorite movies, etc.) anymore without it linking to a page.
Or maybe just 'cause it's the shiniest new toy around :)
A bit like they did in the past with email newsletters. (Though a lot better: for a start, it doesn't spam your inbox, which can remain for more important matters).
Facebook's decision-making will increasingly be driven by thinking like "how can we monetize all this wealth of consumer data" or "how can we introduce tiered fanpage packages to business customers as a revenue stream" rather than focusing on what makes a great user experience.
Currently, knowing that my friend has achieved another 'badge' in Mafia Wars adds zero value to my life. It only gets worse as Facebook focuses more and more on business brands. What do I care if my friend 'likes' Apple or Nike? How does that improve my relationship with that person? People I am really friends with in real life don't care what brands I like, or what isotonic sports drink I drink. The like me because of me. Much as businesses would like to think that people define their lives by the products they buy (this is like the opening scenes in 'Fight Club' where Edward Norton's character tries to pick out stuff from an Ikea catalogue that defines himself) that's not a basis for a relationship. And Facebook used to be all about relationships. Now I look at my Live Stream...and it's got all this random flotsam floating downstream. I care about none of it.
The reason I love HN, incidentally, is because it's the polar opposite of MySpace and what Facebook is gradually becoming. Real people, that I share a lot in common with, expressing their real opinions, no auto-generated crap, and zero bling.
You see comments like "What could cause FB to die?" here on HN. They're so big at this stage, with the power of network effects and lock-in, that external competition is no threat to them realistically. The only way they will die is if they continue exactly the way they are now, making people's experience ever-more spam choked, till people realize "hey this experience is actually quite shit, even if I do have 500 online friends" and start looking for alternatives. We're not quite there yet though.
I think the early-adopter types - like you, me and the typical HN user see real value when it prevents itself, and Facebook ain't it. Mainstream users will hop onto Facebook because their friends are there, not necessarily because it's the best social network out there, whereas early adopters will jump onto Facebook in it's early days because
a) it's cool
b) it's useful - for users - not businesses
c) it's not MySpace.
They will continue to stick around as long as these are still true. Whether a) is still true is debatable, b) is fading and c) is becoming more of a reality by the day.
a) Yes, it's not 'as cool' as before. But, thanks to the 'friends of friends' effect ypu've mentioned, it has achieved remarkable numbers while it 'was cool' - and at this time, that's all that matters.
b) I think businesses are starting to see value in facebook. Facebook Places (with the automatic creation of a facebook page too) will only catalyze this.
And...with a single destination site seeing 500mn+ users, we're in unchartered territory - history won't help us here.
On point b) - Facebook is focusing on making it's services more useful to business, at the detriment of it's core users. Facebook became popular in Harvard because you could scope out that cute undergrad you spotted around campus. The people in your network were tied to your friends and classmates in the real world. The more Facebook grows, the more it devalues it's definition of 'friend' (Facebook's definition of friend that is. Having 300 Mafia Wars friends might make me spend more time on Facebook for a while - increasing Facebook's stickiness, hence it's value to brand advertisers, but it doesn't mean I'll ever have a meaningful interaction with the members of my "Mafia").
Do I want to get notifications every time a 'friend' of mine 'likes' Xbox Live? No. That's not a real interaction - it's just spam. Do I want a notification every time a friend of mine logs into their account in a Starbucks (this is how I'd imagine their location-based feature working)? No. Of course I don't. I want my social network to only give me message that aren't auto-generated, i.e. those that are real messages from real people. Like HN comments.
I think Facebook has forgotten about what made it popular in the first place, and now because of it's size and self-sustaining growth, will implement features that are useless to it's core user base. There will be no telltale indicators (at least externally) of this growing dissatisfaction because any attrition of it's user base will be compensated by new, incoming users. And of course many people who don't like the service will hang around because they don't want to be out of the loop.
What I envision as the ideal would be social networks to emulate email and SMS. I can send a Gmail email to my Hotmail based friend. If I don't like Gmail, I can switch email providers and take my contacts with me. Social networks should organise in 'tribes'. You associate with whatever tribe you feel describes you best. Tribes can interact with each other. If I don't like my tribe (perhaps because it's becoming MySpace-like) I can move easily to another. There could be a tribe that appeals to HN type users, and another for 12 year old girls, and another for retirees. Each have their own identity and values. What I'm describing is an open protocol for social networks, which forces "tribes" (individual networks) to compete on how good they are, rather than how many of your friends are on that particular network. This will keep them honest as they can't depend on user lock-in. In an ideal world, Diaspora and Facebook would be on an open protocol and users could switch easily and painlessly.
Their goal is to capture as much data as possible (updates, likes, places, pages) and to find the connections between things. With enough data and number crunching, they can figure out if you're interested in xbox or Mafia Wars updates or now and adjust accordingly.
Forcing users to 'prune' their status updates is in fact a symptom of something broken in the user experience. I check into Facebook every now and again, and I shouldn't to have to act like a gardener who has ignored his back yard for a month. A lot of status updates are incredibly frivolous too - Facebook's culture is not suited to my taste I guess. Virtually all of my (Facebook) friends are not hacker types and will post "I'm bored" or "feeling tired" or something equally awe-inspiring. Granted, this is something that Facebook would have never solved as they are trying to appeal to the mainstream, not early adopters. I love the fact that by logging onto HN I often learn something new, and quickly learn to a) write well and b) only talk about stuff you are knowledgeable about. Anything else and you will get caught out pretty quickly.
(2) The whole thing about the Dunbar number
This had occurred to me also when writing the original comment, but I didn't mention it as I don't see a decline as inevitable as an online community grows in size - I believe HN is proof of that. By deliberately appealing only to a narrow segment of the internet population through a strict, human-enforced culture (see HN guidelines), and allowing users to only maintain very loose ties if any with each other (contact info in your HN profile for example), it's possible to have meaningful, no-spam interaction on an online community. Pg mentioned recently that HN now gets something like 60k uniques per day. I've been on HN for quite a while and I think the quality of article and comments has been consistent over time. I think the Paul Buchheit philosophy of building something that a small number of people love, and that most people would hate (HN), rather than something that tries to appeal to everyone (Facebook) comes into play here. See my below comment on the 'tribes' concept for a possible solution to this problem in a social networking context. I believe it would work as it models how people organise themselves into groups in real life.