considering how many few rhinos are out there, I guess this is a temporary solution that's just manageable because you can get the game wardens to paint those horns.
The down side is the same for those rhinos that have had their horns medically removed in order to protect them. The poachers will kill the rhinos just so they don't get fooled by their tracks when they are out poaching.
This seems kinda unsustainable..
http://www.bisbeesconservationfund.org/conservation/savetherhino/faq.aspx