Same issue with the ones you mentioned or even ones like G+ that are backed by another big player: critical mass of users combined with no standardized protocol.

I've made the analogy plenty of times before but basically I compare and contrast with email, another service where you can "roll your own" but most general users just stick with a service, either paid or ad-funded, from another company. The thing with email is that it can be 2001 and you're happily using your @aol.com email account but down the line you decide to switch over to Yahoo. Then maybe later you switch to Hotmail and later still, to Gmail. All of those switches are up to the user and nothing stops you from even setting up your own email server if you have the desire.

Regardless, none of the people you email need to do anything or change anything. And it's a good thing too because it would suck if in order to move off AOL or Yahoo you need to convince every one of your friends, relatives, business contacts, and potential email recipients to switch over as well. It might be feasible to get that 5% of your "techie" friends to switch services based solely on some new feature or whatever but you won't have much luck getting Aunt Mabel, your kid's 2nd grade teacher, your barber, or your potential clients to all switch over to some new UI and remember some new account address.

But since email is based on a common protocol it doesn't matter. No matter how popular one provider is, you can switch to any other one and not lose the ability to email. Contrast this with centralized social media and you're basically screwed if you want to switch to another one.

This really struck home when G+ came out. I found it to be a better Facebook for the most part. Faster mobile app, more granular sharing permissions, no stupid game/app spam, better media hosting, and better text/video chat. Maybe 10 of the people I generally connect with on social media felt the same way but the other couple hundred in my friends/contact list? They found it annoying to learn a new interface or they weren't already using Gmail so they'd need to sign up for another account or they just didn't like something else about it.

And that's legit. Variety in services means there will be preferences. But in this case it didn't matter because the end result was the same: unless everyone moved over to G+ (or Diaspora or whatever) en masse, you'd either be cutting off contact with most of your list or you'd be maintaining multiple profiles and sharing links and pics on two sites.

So G+ only got used for more specific groups and niche interests while Facebook kept more general social networking. And now Google seems tired of trying to build a better Facebook and is de-Plus-ifying most of their services. I seriously wonder how anyone will conceivably succeed at this where massive companies like Google can't pull it off.

Instead, just as centralized social media replaced mass email chains for most people, I don't see Facebook going anywhere until something entirely different (not just new and improved) comes along and grabs mass user attention in the same way.