Interesting... Was talking with a friend today, and she was telling me that with her friends (& amongst younger friends/siblings/etc), they now don't really 'use' facebook, because it 'was' cool, but now is 'boring'. From my observations I was starting to see the same thing (obviously there are still a lot of users, but not necessarily 'active').
Interestingly enough, doing a quick check on Alexa shows facebook appearing to 'peak' traffic wise, so maybe 2011 Facebook will be kind of like what infospace.com was to Google. (Infospace/the 'go' network was 'the' place to search, until Google replaced it).
Do you think facebook is now becoming just a passing fad?