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.
I've said it manytimes in the last few days, but it bears repeating. The thing that makes Flickr so interesting is its broad and stable API.