"I'm pretty sure back-alley surgeons will start removing these tags from illegals as soon as they are introduced. Plus, RFID only works relatively short distances from the scanner so it is only useful for access purposes and not as a beacon. It will only inconvenience legal visitors. There's lots of different sorts of RFIDs. I wouldn't think these would be implanted. More like a bracelet or anklet with a bigger battery and longer range. Add to that an "electronic seal" so that if it is removed, it automatically "calls for help". That way, you catch the "about to become" illegal, and anyone who is helping him/her.
It's not perfect---just another tool.
DNA.... In 5 years identification will be 100% accurate and instant. I suppose I can think of a dozen different things people might do, to try and fool the test, blood dope with someone elses DNA? plant someone elses cheak cells, but I think DNA will be the answer ultimately, maybe a thumbprint + DNA + Iris Scan And it goes without saying all of this would be more effective with an aggressive racial profiling protocol. Travel being what it is, there needs to be a unified global system. Scary to some, but inevitable yah? I'm authoritarian, I like all this stuff. (Not a popular sentiment around here)
But I wannna catch all the scumbags, let God and Barney Fife sort 'em out. The RFID chip would be good if it could be injected deep into the brain where it couldn't be removed. (kidding) NOT!
-I- would issue Fife all 6 bullets... :-)