In this case, a mix of both is required. While you absolutely must plan ahead and implement as many safeguards as you can prior to launch, that's simply the beg

In this case, a mix of both is required. While you absolutely must plan ahead and implement as many safeguards as you can prior to launch, that's simply the beginning, and it is incredibly naive to think that all the leaks can be prevented. (Or, honestly, that really any aspect of a community can be perfectly master-planned in advance.) To operate anything like a UGC platform is to be eternally engaged in a battle against ever-evolving and increasingly clever methods someone will come up with to exploit, sabotage, or otherwise harm your platform. This is totally fine -- you just need to acknowledge this and try not to drop the ball when things seem like they're running smoothly. Employing every tactic at your disposal from the very beginning should be viewed as a prerequisite, one that will start you off in a strong position and able to evolve without first having to play catch-up.