The problem is, each 'viewer' application (Facebook, G+, Twitter, mutt, etc.) has an incentive to add proprietary features which only work on their system. Not only does this differentiate them from the competition, but it's also an easier problem to solve than if they tried to make it distributed (e.g. Facebook can add features to Facebook much more easily than they can to email, since they store all of the Facebook data and broker all of the Facebook messages; their only problems are how to make it appealing to users and cost-effective to run).
Over time, the walled gardens return.
In fact, we've basically seen this happen before: many people ran their own standalone Web sites on their own domain. The "viewer" was the user agent, which could be your choice of browser, aggregator, etc.
I think the killer feature of Facebook over standalone websites and blogs is that with Facebook you can choose who is allowed to view what you post. Maybe I'm wrong, but I remember people being a little uncomfortable posting pictures of their kids on a blog for the whole world to see. With Facebook, only your friends are going to see those.
> with Facebook you can choose who is allowed to view what you post
Well that's their kool aid, which many people have been drinking.
I still follow the rule that you only post stuff online that you're comfortable sharing with the world: it's not a matter of if the databases will be leaked, but when.
> Maybe I'm wrong, but I remember people being a little uncomfortable posting pictures of their kids on a blog for the whole world to see. With Facebook, only your friends are going to see those.
Use a blog software that allows to enable viewing of some content only to users that authenticate (for example via OpenID) and are of course in the list of allowed users (that you carefully maintain).
Over time, the walled gardens return.
In fact, we've basically seen this happen before: many people ran their own standalone Web sites on their own domain. The "viewer" was the user agent, which could be your choice of browser, aggregator, etc.