I'm pretty confident about GOC's privacy policy and it being respected.
However, like SantaClawz, I have concerns. No internet site is totally immune to breaches, hacks or data theft. If 1000 members enter the contest and the data is stolen, that's 1000 addresses in the field which the robbers know there are guns at. I don't want my address on that list, thanks.
SantaClaws suggestion is a good one. You should think of a way of making this safe for the participants as much as for GOC.