Well, one risk you run is that you'll end up a repeat of the Yahoo! debacle. I think you can probably avoid that by being up-front that all reporters will get is swag, and that this is because you have no budget for a bug bounty but want to give them a token of your appreciation.
I think the bigger risk is that without a financial reward, the quality of the folks looking at your stuff is not going to be as high, and there won't be as many of even the amateur folks.