[nostrademons]

Hard lesson learned through experience: if you're phrasing the question the way you have, you've already failed.

Viable ideas usually come out of a community that's at the forefront of some change in the world, either technical or social. Embed yourself in such a community and then build what you and your friends need, and chances are the rest of the world will eventually come around to seeing they need it too. If you're explicitly trying to brainstorm and evaluate ideas rationally, particularly if you're doing it in isolation, you will a.) bias yourself toward ideas that sound good but aren't what anyone wants b.) bias yourself toward ideas you might've heard of in the press but are already filled with competitors and c.) bias yourself toward ideas with big potential markets but that nobody actually wants.