Strange how the people who generally mention the overpopulstion problem are also opposed to war. That tends to be the world's answer to overpopulation. Famine/desease/natural disaster/war tend to trim down our population. If we become too overpopulated, someone comes along and says, "Hey, we need some room." the other country says, "You can't have it." The first country responds with "These destructive devices say I can." Then we get war. Lots of people die for their countries, and the population comes back down.
I honestly do not see us having an overpopulation problem. If anything it is an innovation problem. Too many people complaining about the wrong problem, and not working to fix the right problem. Rather than complaining about the "too many people" problem, shouldn't we be working on the "not enough food" problem, or the "not enough room" problem. Seems to me a better approach than "You can't have more chillunz" which is rather difficult to enforce.