A recent Lifehacker story about a Greasemonkey script to remove quiz stuff from Facebook made me realise something: you know your site is too "web 2.0" when users are going out of their way to remove features. A quick search on Userscripts.org reveals that a substantial proportion of the Facebook-related scripts are either for removing features or auto-playing game applications.
I feel that Facebook started off pretty well. The initial target audience seemed to be students, and that's what most of the users were. It was friendly and uncluttered, compared to other social networking sites like MySpace. This spread to a wider audience, first sucking in kids and then adults. This was less than ideal for some, the idea of their parents on a social networking site being horrifying, but still not a disaster.
But in the midst of all this, the apocalypse happened: a powerful API which allowed other people to extend the functionality of Facebook by creating applications that people could add to their account. Gradually users became inundated with an unstoppable torrent of application requests, caused by application developers making the "tell all your friends" step seem (or be) necessary to using their application. The average user's profile became a mess of applications competing for screen space. The target audience became those who have the time to play endless Flash games, answer endless quizzes, and generally clutter the "requests" page of their friends.
And so Facebook became MySpace 2.0---gaudy and cluttered, with infinite ability to add more clutter. Maybe the lesson learned is that the moment you allow anything "shiny" in a social networking site, your demographic will degenerate to schoolkids who want to fill their profiles with as much of it as possible.
Personally, I've reduced my Facebook interaction for the past 2 years to having the site email me when anybody says something directly to me either via message or on my "wall". There is just too much clutter now for me to wade through the endless application requests, friend requests from people I don't know, and news feed items generated by the latest viral quiz. And maybe pictures of friends getting drunk have lost their novelty value...