lucky, it's a bad move to sell information on the play. You don't know what could happen. How many people is that person going to tell? To many pigs at the trough can get a play squashed quicker than anything else.
This is correct. I've seen this happen all too many times.
You're best off giving it to someone you trust (or at least semi-trust), in exchange for part of the action and/or flat payment, and then getting a promise from them that they will tell no one else.