My dad's doing a report on this for work, so I know a ton about it.
Advantages:
Tracking lost kids down
No more keys necessary
Your car, wallet, bike, credit card, gun(police are starting to use them), will only work if your chip is within feet of them
Disadvantages:
Possible infections
Rely on electricity more
Locked out of house if there's an error in the system
In my opinion, nowdays they don't need to have it attached to your nervous system, which 10x lowers chance of infection, and makes it well worth the risk. The only problem would be today's computers level of reliance. They fail too often for it to be worth it. Maybe in twenty years, but not now.
www.gameroom.com/blinkcomic