If that's true, I don't think you need to worry about people "stealing" your idea. Most people don't have the drive to stop what they're doing follow through with someone else's idea just because it sounds nice.

My advice is to feel free to talk about it and gauge interest. If you're that worried, just choose who you share with wisely (don't share it with people currently looking for an idea to work on), but I really doubt it will be an issue.