Okay. I've spent a few weeks on Facebook and I think I have a good sense of its pros and cons.
First of all, it IS a wonderful way to keep casually in touch with people, usually in a cute and noncommittal way. You can find out what people are up to, remind them about upcoming events, share pictures with them, and basically take care of all the stuff that you'd never bother calling or emailing about.
The thing is, some people are VERY ACTIVE within Facebook. They're constantly posting updates, adding applications, and joining groups, and every time this happens you are notified about it. Not coincidentally, the people who do this frequently tend to be the people I am only tangentially friendly with, so I spend my Facebook sessions being bombarded by crap from people who I care little about.
And I'm automatically distrustful of these applications I'm always prompted to install. I doubt there's any security risk involved, but in my opinion they're just useless clutter that I'll never use anyway. Why do I need a special application in order to get a pleasant message from somebody? Why don't people just send me a nice email, instead of forcing me to install a "good karma" application?
I suspect the answer is because the applications are one step further removed from regular human interaction. If somebody sends me an email saying "you're hot," I am generally creeped out. But if they prompt me to install a "you're hot" application -- and I know that all of THEIR friends are being prompted to install it as well -- it stops being a REAL message and becomes something else, like a happy wave or a drunken "cheers."
Obviously there are many different ways of looking at Facebook; some people see it as a vibrant community, some as a lifestyle, some as a networking tool, and some -- like me -- as a way to maintain casual contact. And since I'm bad at keeping in contact this is a good thing, but I REALLY don't want to be reminded every time somebody I barely know is washing their hair.