I was having a chat with a coworker who is working on a polling app and framework. He was asking technical questions and I suggested he open source the application to get more quality opinions from developers who are interested in this problem and are willing to give it heavy though.

He has a different point of view which I think is still valid so I want to open this question for discussion here. He says he believes something like a polling framework should not be open sourced because it will reduce its security and validity as people reveal loopholes through which they can cheat. Can't say I completely disagree. I see a somewhat valid point there, but I always believed that solutions by a group of people are almost always better than a solution thought by a single person asking a small number of coworkers, no matter how smart that person is. Again I'm willing to accept that maybe some types of applications are different.

Does anyone have an argument in his favor? I'd really like to present your responses to him.