Between feature bloat (Facebook's trying to be everyone's portal to the web, and it sucks at it) and the constant middle finger they give to users via security issues and privacy settings, it is a wonder I still use it. But like many who make excuses, I run back because it offers one simple access point to the majority of my friends. If I didn't hate making phone calls, I'd likely drop Facebook...damn them for cornering the social network market for the time being*.
Side note: Been using FB for at least five and a half years and honestly most of what they've done in the last year and a half has only annoyed me. I can understand UI improvements and other elements they've adjusted/added over the years, but the last two iterations of their site design are trash compared to their previously efficient layouts. Of course, one could point out that the last two designs have been more about advertising and games (aka profits) than usability for the users.
* - Like the majority of things on the Web, at some point it will be beat.