If you invite anyone to the party and don’t check their bags at the door be prepared for a very big clean up when it's all over.
I’ve witnessed and participated in the Human Rights Logo competition which claims to have gathered over 15,000 entries. As sincere as some of the submissions were, many other submitters simply gamed the system, “borrowed” ideas, or used the forum to express their negative world views.
Months of infighting, self-serving critiques and non-sensical submissions yielded little in the way of innovative design. Crowdsourcing this task was probably not the best approach: it would appear that some entities decide to “crowdsource” without developing a system of checks and balances to get the most positive work out of their community. Crowdsourcing does not work without real crowd management.