Not that it isn't great for stuff, clearly people are doing fine with it.
But for me, it is mostly aggravating.
1. Please don't ever send me a Facebook message/invite/whatever and expect I got it. If you actually know me and it is actually important, then you know how to contact me via Email/chat/cell phone. Doesn't everyone have a email filter setup to automatically dump anything from Facebook?
Do this: Skip Inbox, Apply label "Facebook"
2. I don't want everyone I ever met knowing the random thing I might have posted on Facebook while out drinking. Facebook has these Friend Lists, why can't I setup permissions based on them? All I need is a set of people to which I post anything I want, and another set of people who don't get my posts/pictures/whatever. These set of people is really the 'business card storage' group.
3. While I'm not going to lengths to protect my identity/personal info on this blog, I'm not exactly broadcasting such information either. I have no problem with people being anonymous on the Internet. My picture isn't even here. Is nobody else a bit torn about internet anonymity? I don't really want my digital interweb existence to be an extension of my real world life. I want it to make my real world life easier. Maybe I just watch to much Battlestar Galactica, but I really don't need a virtual copy of myself floating around the Internet trying to become self aware and going all MCP on me.
4. I'm not paranoid.
5. I tried setting up a 2nd Facebook account using a pseudonym, but they go to lengths to stop this. I can't link two Facebook accounts to 1 phone number or the same email address! Argh. Plus the confusion of having to figure out which account i'm dealing with is even more aggravating then dealing with 1 Facebook account. This is right out.
6. I use plenty of other social media tools. Like this one I'm typing on right now. Twitter is useful when used appropriately; I like the simplicity. Google Buzz makes my life easier, although its a bit limited at this point. LivingSocial deals are kinda like social media and they save me money! Facebook costs me time. LinkedIn is a boon.
7. Pretty sure I'm not paranoid.