I recently decided to join facebook (to be precise, right after reading Lauren's blog). So far it seems like an interesting little social tool, that benefits hugely from it wide support in the academic community.
What make facebook really interesting (in my mind) is that it is actually an application platform or - to use a now unfashionable term - a programmable portal.
THis feature really enable facebook to mash-up all kinds of services (Amazon, Dopplr, Google Maps, del.icio.us, to name a few) and present them in a fairly simple UI to users.
A downside (at least right now) in my mind is the insane default privacy settings: If you do not change your default privacy settings: If you do not change your defaults, your data is pretty much exposed to anyone, anywhere (especially since joining a regional network is rather uncomplicated). While this might have some appeal for college students, it is the single biggest issue that I have with facebook - and probably one of the most important reasons why facebook (and MySpace and other social networking tools) got a fairly bad reputation. Sharing personal information by default without EXPLICITLY opting-in is a bad thing.

Interestingly enough, you can extrapolate from facebook et al. to legal standards in general: While the U.S. has largely an opt-out approach to sharing personal information, the E.U. take a much more restricitve opt-in approach^[1].

tag: facebook, privacy, policy

[1] Except when dealing with the various governments - in that case there is pretty much no opt-out at all available for European citizens (e.g. the German GEZ will be able to get all kinds of very personal address history data from town halls and central agencies).