Not too mention facebook completely changes in design and is constantly evolving its look. If FB still looked like how it did in it's early inception I doubt it would be as popular.
Perhaps there is some study to be done where social sites/apps become obsolete if they fail to adapt their UI/UX over the years. I mean look at sites like Fark and SA compared to what is popular nowadays like Snapchat or Reddit.
Reddit? I see lots of comments about how people are amazed Reddit has remained (or, really, grown) as popular as it is while still having a very "low rent" UI.
I'd actually argue hallelujah that reddit hasn't significantly altered their UI. It may not be pretty, but it doesn't take that long to get used to its quirks, and when you do it is extremely fast and easy to navigate and find meaningful content. I contrast this to slashdot, who proceeded to make their UI WORSE with every update (more "modern" styling and response, but they made it totally broke the usability of their commenting system).
I find the problem with Slashdot the fact that they've updated their styling to be in line with what was popular in 2006, with a commenting system from 1995. I can't read their comments any better than I can read mailing lists; they're both horrible, horrible ways of displaying conversations. In my opinion, their commenting system has been broken since I started reading the site back when CmdrTaco was still unmarried.
I left Slashdot because of the rampant censorship; if you ever posted something going against "prevailing wisdom" even if completely true, you might have found yourself unable to access the home page for a day and your submission ended up deleted. On completely factual, verifiable things, not politics/gender/whatever controversy.
Perhaps there is some study to be done where social sites/apps become obsolete if they fail to adapt their UI/UX over the years. I mean look at sites like Fark and SA compared to what is popular nowadays like Snapchat or Reddit.