I bumped into this web site, Minor Delays, I think it was on metafilter. The author aims to provide a short story for each station on the London Underground. The one story I looked at looked interesting, but I can't say I've spent much time on it yet. It's just that the idea sounded interesting.
Some days everything I encounter sparks a story idea. And a lot of the story ideas, even the ones I end up writing down, don't make any sense to me later. They represent fleeting interests or enthusiasms. My current conviction is that the most important thing about a story idea is that it interest you enough to get you to finish the story.
I'm much more interested in story structure now, and believe that any story idea that is to be turned into a real and satisfying story must have a lot of work done to it. But that doesn't make me any less subject to fleeting enthusiasms.
I'll throw a small amount of work at almost any idea that I like, but on the other hand I've got several stories that I've been writing and rewriting for years. And the interesting thing here is that is still get a big kick out of working on them. Some of them are probably stories that I should just abandon. I've got one that I've abandoned several times and I still come back to it...still trying to get a solid story out of it.