The issue is assholes entering the intersection to turn left when it isn't clear...
This general idea is one of the biggest issues that I see with traffic problems. People for some reason either don't agree on what the law is (as a further poster notes, it's legal and encouraged to enter the intersection for a left turn in many states if not all in the US), or just don't know. Now am I a perfect driver? Not by a long shot, but the fact that people have different ideas of what the actual law is while driving is one of the most concerning (and at times frustrating) thing to me as a driver.
The government could also keep track of who was purchasing and using drugs.
This would be my concern. If I want to take drugs, am I really going to be interested in going into a government sponsored building to take these (Note: I don't actually take drugs)? The stigma itself may prevent some, and the fact that the government is tracking it could really turn others off too. That's why I wonder if this was done, would it really prevent people from getting drugs in other illegal ways, just to hide the fact that they are doing it? I'm not against legalization whatsoever, it's just that I'm not so convinced that it would 100% fix the problems we currently run into today. I think it could certainly solve many problems, but I don't think it's a magic bullet.
The computer is to the information industry roughly what the central power station is to the electrical industry. -- Peter Drucker