Well, this is the first time I've been engaged in an extended conversation on HackerNews (not sure when I first started here, but it's been mostly one-offs and very little back and forth up to now). Excuse my shock - was a bit rough, but consider me initiated.
I've been pretty anti-Facebook for quite some time, far before it was cool to be anti-Facebook, so I'm probably carrying some baggage there as well.
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To your points - I think that MySpace v. Any Other Social Network in 2005 and MySpace v. Facebook in 2009, 2008, or 2007 are two different situations entirely.
MySpace WAS Facebook in 2005. Facebook was something else entirely - some sort of exclusive social network you had to be a college student to use. I didn't fall into that demo, so I couldn't use it at the time, being far past college age.
If you compare the two networks now, it's hard to imagine that they're both supposed to be the same class of website. MySpace has let design-rot take root like a bad termite infection. It has problems going back to its inception with spammers.
Facebook doesn't have those problems, and it's working well to ingrain itself to the fabric of the web... but it's not making money, and they seem to have the same disease Twitter has, which is this lack of hunger for picking the low hanging fruits in terms of viable tried and true monetization methods.
I wrote on this at some point when I was at Mashable - when we were all theorizing as to what Project Beacon was going to end up being. My theory, which was way off as it turns out, was that they were building an offsite behavioral ad network that webmasters could use in the same way they use AdSense. They're slowly crawling to this now, I hope, but they're a long way from it, and it's the one killer app that could strike a blow at Google's AdSense and capture a SIGNIFICANT share of the worlds web ad market.
Instead, their content to run what basically amounts to poorly targeted remnant ads INSIDE THE SITE, where they're least effective.
I'll put it this way by giving you an example from an unrelated series of posts I did way back when splogging was a majour scourge on the net. Remember those search engine results we were all getting several years ago that look like a monkey wrote the blog posts? You'd search for "underwater basket weaving" and you'd get a splog with that as the title, and nonsensical computer generated blog posts surrounded by adsense ads?
They worked and made money for the sploggers because the content wasn't what the user wanted to see, and most surfers are as likely to click a relevant link as they are to hit the back button.
Facebook content is too good for ads to work. When I log into Facebook, I'm looking at what I'm there for because it's content tailored to me. All those pageviews mean nothing for ads because I never get bored enough with the content to click on them.
The wilds of the web are much different - content on the web coming from search engine results has varying degrees of relevance to me as a searcher, and ads are much more likely to be clicked.
All this to say that Facebook may be great and all, and they may have the greatest momentum ever, but if they don't get serious and look at the BASICS of how their monetization model works, they're not going to get anywhere. I've been banging this drum since early 2007, and it's frustrating as hell to see so much squandered opportunity. Going on a hiring spree and re-arranging the UX won't fix that problem, and that problem is the crux of what makes a business... money.