I do the same thing. I have different groups of people and just talk over email threads. Works far better than G+ or FB.
I've been thinking about how to fix email as per YCs list of things they'd like to fund (just to get the juices flowing) and it might be cool to build on top of the email protocol rather than replace it - e.g it's trivial to format, say, todos in an email in a human readable format such that they can still be read and returned checked off by users who don't use this additional layer.
The first, more concrete, set arises simply because of the age of the protocols. They were developed when the internet was a club of like minded people rather than a global public space. Things like: a lack of rock solid authentication, no guarantees of transit privacy (much less at rest privacy), clunky formatting, multimedia and hypermedia support, arcane attachment problems, and only hacked on support for anything beyond 1:N messaging (e.g. mailing lists).
A lot of these problems have good, solid, proposed solutions but inertia and collective action problems mean that near universal support for protocol additions / changes take years if not decades.
The second, more amorphous, set of problems have to do with how some people use email pervasively in their lives in a fashion that (inevitably) would be more efficiently accomplished with a tool specialized to their needs. So for example, people who spend a fair amount of time in a corporate enviorment with Exchange often bitterly miss the calendar management integration. They say that vanilla email is broken because it has no equivalent capability. Although the critique is legitamite I think the target is off, it's not email that's broken, it's federated calendaring in general. But because email can sort-of, kind-of substitute it gets the blame.
(Which doesn't help if it wasn't you who sent the original mail…)
every post on your news feed has got a tiny "hide" link, which you can use to either unsubscribe completely from a friend's wall posts (yeah, keep those "how I met your mother" quotes for yourself bro), choose which kind of news you're actually interested in (pictures only, events etc.) or even choose how often you wanna see a person's posts ("all updates" or "most important"). if you get the tendency to disable a post that you don't like the moment you see it, then (on the long run) you'll end up with a wall that's at least 2/3 interesting or let's call it decent (facebook is not really hacker news). I'm not aware if this is the actual implementation, but would be really cool if Facebook would actually learn from the posts you hide and stop suggesting similar ones in the future.
I've got around 300 friends and had I not unsubscribed from a lot of them, my news feed would have been packed with wedding pictures of people I don't know, events I can't go to or causes I don't really care about.
just to end here, email has its purpose but that purpose is not social sharing any more. just like emails took over writting letters years ago, social networks should improve over emails in the aspect of sharing information with ease. oh, and to the author: the facebook experiment hasn't failed - you just need to tell it what you expect of it.
People expect that Facebook provides the automatic content customization/filtering. And rightfully so, I may add. It's a shame that Facebook is little more than a walled-garden email service with photo storage.
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...