consider this: all your Facebook friends decide to start emailing each other pics of funny cats instead of posting them on their walls. you're a friend, so you get added to the CC. wouldn't it be the same amount of work to filter through all this content for relevant information?
I'm not a big fan of Facebook (especially because of the news feed ads), but most of my friends are camped there, so the only thing I can do is try and get the best out of it. I do enjoy email conversations with my friends (mostly with my programmer buddies), but the replies tend to be a bit slower and the stories never get so many follow-ups as Facebook posts. also if you want to email pictures, you'd better use a different service (Picasa, Dropbox) if you don't want to download zipped files all the time. same for videos...
to make this clear, I'm not advocating for Facebook here. I just find it curious to read something like "the facebook experiment has failed", when there's no interest in the author to see what the experiment has to offer. more specifically to try out some of Facebook's features (some of them are really obivous, some are implied, some are more difficult to understand).
when you've got 1000 friends but you're not really interested in anything they say, who's fault is it?! and yet Facebook gives you the tools to filter them out...