I wonder how different it really is - hanging out in facebook, or hanging out on a forum or blog.
Been using the internet for a long time, and at any point in time I usually had one web forum where i tended to hang out. Many years ago it was LucasForums, more recently it's been GOG, and there have been many in between.
While I joined each forum for a reason - a current interest, or needing an answer to a question - if i got involved in the community and recognised the members then i'd tend to check the forum when i went online, and check for new posts, follow any links that looked interesting, etc... whatever the purpose of the forum, there tends to be a General Discussion forum, and that tends to be people talking about movies, music, games, recent news, and posting random weird web links.
Is it much different to check into Facebook and talk about movies, tv, recent news and random web links with contacts there? I'm not sure it is. The main difference would be that the people there are real life acquaintances, whereas i've never met anyone off any of those forums. There are pros and cons to both.
Personally, I rarely surf totally randomly - i'm usually searching for something or checking regular sites. I do get distracted a lot though.
I don't get much value out of facebook, as i suspect it depends totally on your friends. My best friends don't use it, so most of the updates i get on it are from distant acquaintances about topics that i'm not hugely interested in. I imagine that if i had a big group of close friends who used it daily then it might be a gateway to more interesting things.
Twitter - it's getting close to replacing RSS readers for me. Not because it's more efficient, but just because it's something new that does the same thing.
(sorry for the epic post!)