Very similar is the recent story about people with toll pass devices being pinged while in NYC streets. Even if the intentions are pure, the systems could definitely be abused in the future by law enforcement or hackers... I'm actually for the use of this kind of technology for law enforcement, as long as they are targeting actual criminals. The problem though comes back to ethics and the fact that there are enough unethical people in the world that they seriously need a higher power overseeing everything they do.
If you've been to Disney World in the past few years, they're doing the same thing using the magic bands....If you have a simple ticket, it's passive RF cards. The Magic Bands are battery-powered and have greater range...they open hotel room doors, can charge items to your hotel room, and can be linked with park tickets and photos they take of you in the parks... I would assume they have long-range readers that can do rough counts on how many guests are in a particular part of the park. On some rides, they take your picture and know automatically who was in the picture based on the magic bands. It's pretty cool.
They were using similar technology at the Super Bowl a few years ago with tags placed on jerseys....then tracked player speed and position on the field using a reader from above the field.
Honestly though, I'm assuming these RFID chips simply have an encoded number on them. As long as the number is local to their DB, no one else could really use it for anything if they happen to read it....unless they know how to cross reference the number to the person....or track how many times they see the same number in an area using a reader.... Also, these are likely full-passive RFID chips, so they don't broadcast or "wake up" when pinged. You may have to be within 6" to read the signal. The technology is going to evolve and change....but there's not much difference between this chip versus a card, except for the fact that it's injected in you, rather than in your wallet. Eventually, when readers become more advanced and more data can be stored on the chip, things could get messy. Hopefully the feds won't soon start injecting babies with chips and selecting what jobs people are going to do when they're born....it'd be like that Ayn Rand novel.