Last weekend I was at a friends place, and there were a few people there. One of them asked me what I did, and I told him about an idea I had for a new way of doing business online. It's pretty revolutionary, I've thought long and hard about it for a long time, and it can probably be easily copied by someone else. I told him about it anyway. Pretty detailed too.
It just happened that he was finishing up a PHD thesis on a subject very close to what I was thinking about, and we started talking. This conversation gave me some great insights I didn't have before, access to his large network, a serious ambassador and maybe a friend.
Will he steal the idea? I don't think so. Empirically it is very very rare. Did I gain something from it? Absolutely.
Answer enough?