I'm uncomfortable when people want to volunteer their ideas to me for exactly that reason. There's also usually an implicit question: how much will it cost you to build this for me?
Rather than hearing someone's idea for an app I'd much prefer to hear about an existing, unsolved problem that they have. You know, an actual problem worth solving. Those tend to be the more fruitful variety of ideas, IMHO.
I had this friend who called up to talk about an idea. I listened for about 20-30 mins, made what i thought were meaningful questions, then asked him, i have an idea too and if he wants to listen? He said, he'll call back in an hour and was gone. I guess, he wanted me to execute the idea:-). Btw, am working on implementing that idea of mine, only it's going slower than i would like it to.
Rather than hearing someone's idea for an app I'd much prefer to hear about an existing, unsolved problem that they have. You know, an actual problem worth solving. Those tend to be the more fruitful variety of ideas, IMHO.