Putting your idea right there in front of some pretty fast moving programmers has to be something people would think twice about.
Having said that, it's hard to imagine an idea being sufficiently compelling to start writing code to implement it immediately. The only ideas that really blow me away are my own and they usually turn out to be silly anyway, after I've spent six months building them to crickets.
I don't think ideas are worth nothing by the way. Just ask the Facebook twins.