While wheresgeorge hasn't been entirely "cleared," they have been directly investigated by the secret service and the only fallout was that they were prohibited

While wheresgeorge hasn't been entirely "cleared," they have been directly investigated by the secret service and the only fallout was that they were prohibited from selling stamps directly. It is not permitted to advertise on currency, and they considered this to be promoting the practice. Individuals marking their own bills for the purpose of tracking them however was considered a separate and fully permissible action. The legal standard for defacing or destroying requires that the banknote be made unfit for circulation -- though that is about as clear as mud, it has been a pretty tall standard to meet.