A thought just popped into my head when Peter Rojas friended me on Flickr.
I wondered what if we used Flickr's API to implement a message system that worked like Twitter, with a timeline, and of course great picture support. Does the API have enough juice to do it?
I think a lot of it would depend on how much of a moving target the API is. If it's not moving, at least for a couple of years, it might just work.