That's a fair question - however, I'm employed full time and just can't spend all of my free time working on apps, even for money :)

But you do have a good point about someone else possibly seeing value... however, many of the ideas I've been approached with are of the form "like Twitter, but for Poker players!" or something similarly silly.

The problem I see with these types of projects is that they are typically championed by people who have no real understanding about how software is developed, a la clientsfromhell.net. Those are situations I just don't want to get involved in.