So, why not wait for it to be a problem?
FAA has historically taken this approach towards regulation and they catch flak for doing it that way, too. Many of the FARs exist because someone died doing XYZ in or with an aircraft, so they made a new rule that says you can't do XYZ in or with an aircraft.
RC aircraft have been a hobby for many years and most enthusiasts stick to a stringent set of (voluntary) safety rules developed by the Academy of Model Aeronautics. Now that "drones" have become popular, widely available, and relatively cheap, thousands of people are playing around with them and they aren't the responsible hobbyist type. You can get a camera capable quadcopter for under $100, they even sell one model at Wal-Mart. Many of the folks buying these couldn't care less about a voluntary code of safety, and I'm on the FAA's side here, there need to be rules with teeth to back them up.
Putting anything in the air for commercial purposes has always been heavily regulated and I for one don't see that as a problem.