I know some will say I am paranoid but I was reading today about ADS-B and recalled that it had been brought up here before. I also recall seeing an article about someone developing a similar concept in a much smaller package that would be suitable for RC use. Based on other FAA documents I would not be surprised to see some regulations along these lines come out in the not-so-distant future. It's somewhat inevitable as long as there are those who insist on violating Class B, C and D airspacees and the Class E airspaces referenced by the ADS-B requirement.