One of my class mates is a bit paranoid in my opinion. He believes that the American government wants to implant microchips (RFID chips) in every human on earth to keep track of them, and implement one global currency. So on this chip, you will have your money to automatically pay for stuff etc, bus card, medicines, GPS tracker so the government knows where you are etc.
Then the government could turn off the chip remotely if you break any law, and what I understand, kill you.
Now for me this seems kinda unlikely because: Why would the American government do this? Also, RFID chips isn't too secure. I seen vids and news articles that you could clone RFID stuff easily. Like those cards you use to get into certain buildings (school, work etc), I've seen reports on people reading them using their own scanner to get the ID, then making a new chip with the same info. Well, then identity theft and robbery would be soo much easier. They had an entire Mythbusters episode on this, but they weren't allowed to air it.
His source: http://www.youtube.com/watch?v=vuBo4E77ZXo