As a programmer, I would be much more inclined to help someone with an existing coding project than to build a prototype for somebody else's idea.

I can't nail down exactly why, and I'm just a single data point.

I think with myself it has to do with how invested someone is in a project. If they're really into it they'll have some kind of prototype put together and it shows they invested serious time in the project. I don't really like putting together a prototype for someone else, then having everyone else abandon it.

Thanks for sharing, how did it turn out for you afterward? And even if it doesn't work out for the first idea, did you find your skills useful for later prospective ideas and partnerships?

So far I made one iPad game which turned out to be pretty decent considering that I didn't even know what I wanted it to be when I began. Now I am myself sure I can build a prototype of pretty much anything not insanely complex (and I barely coded at all 5 months ago). Not sure I am going to do games further because I don't really understand how to market stuff that does not solve problems, but still it was a valuable experience.