Let me start with a disclaimer: I use Facebook, but I don’t like it much!
So why use it? With Facebook you can do most of the possible things in social media, you can blog, microblog, chat, photoshare and use it as a newsreader. It will also attempt to integrate (read takeover) programs such as Skype. The trouble is, it does none of these things very well, but it does do them all in the same place! This is convenient.
However, if you are strongly into photosharing, Flickr is a much better choice, similarly for microblogging, Twitter would be the go and for blogging itself? Gosh, perhaps a blog would be better?
I use it myself mainly as a newsfeed from media sites both in Australia and from overseas and as a way to keep in desultory touch with friends. Given the number of ‘friends’ I have on Facebook and the number of extraneous sources, causes and interests I track through there it produces a comfortable ‘feed’, one which I am able to look through so that I don’t miss much.
With Facebook I think it’s best to look carefully at the Terms of Service. I certainly don’t post any photographs there that I actually care about.
Worth a look is this.