Unlike the book business, the film business is conceptual not literal, which puts ideas at greater risk of "theft". Does this concern you?
No, because no one can tell my stories the way i can =D. I believe there are few original ideas. Its a person's unique take/perspective/style/etc. That makes or breaks an idea.
If someone tries to steal my ideas, I will go ballistic on 'em! LOL...but seriously, only a total jerk would do such a thing. I copyright my stories to be on the 'safe side'. Besides, everyone has their own voice and every author I've ever read does not write the same as another...except Stephen and Tabitha King.
Going ballistic has a way of alienating people-that's got the sort of splenetic splash that leaves a sour sense in someone's mind. Going with an intellectual property attorney has a way of having people go with you right to the bank.
Yes, it's a concern. I have a situation right now where someone "lifted" someone's project, so they say, and they're negotiating a settlement. The film business, sometimes is hyper-literal, and submissions and pitches are recorded, signed for, and sometimes even made with an attorney present.