I had an idea which I thought at the time was novel. I haven't worked out all the kinks in it yet, but if it could be made to work, I think it could be awesome.
It starts with a home server, web-facing and firewalled against casual intrusion. You keep your data on that in some standard configuration which lets outside companies tap into and add value to the data of everyone who registers their servers with that company.
Example: Photo-sharing on a social network. You'd have your pictures on your home computer in a given format that the outside system could read. You'd register your server with flickronlylessskeezy.com, and users on that system could see your pictures, comment on them, etc. The second logical step would be to register your home server to hold the lists of friends and comments.
Advantages: The data would stay on your computer. You control who does and doesn't access it by registering and deregistering outside services and controlling privileges, and if the service goes down, all that's lost is an accessor method; your data is still in your control. And if some organization decides they absolutely need to take down some incriminating or inconvenient data, an attack on a single server will take care of it without damaging the service for everyone else (beyond not seeing that special data).
Disadvantages: It does require either static IP addresses or tracking back through dynamic IPs, and more than a little computer knowledge on the part of the user, including database management, although with some very specialized software, there might be ways to make this user-friendly. It would also benefit greatly from decent connection speeds and ISPs who don't throttle "power users" (which right now is damn near none of them). And some companies which get in on this might want to stifle competition by using non-standard or proprietary data formats, which means if the service goes down your data is stuck in a black box which you can't open.
Well, once those problems are cleared, anyway, I think it could work. Thoughts?