Jim Harper is the author of Identity Crisis: How Identification is Overused and Misunderstood. Jim is an analyst at the Cato Institute, a non-profit thinktank with Libertarian leanings. Phil Becker introduced him by saying his book was a great introduction to the theory of identification.
He uses the discussion of a national ID card to launch into a discussion of identification and it's theory. There are serious challenges in identification and policy makers will do a better job if we do a better job of articulating what identification is, how it works, and why it fails.
Surveillance is easier if we have a universal identifier because databases can be more easily correlated.
Access to data by a government puts that government in a better position to affect your life. In true Libertarian fashion, Jim lists the negative implications of that statement, but I'm sure more liberal interests would also list positive aspects. With more data, you can warp the incentive structure of law enforcement because you can use the data to determine that someone might have broken the law and then go look for the evidence. He cites highway data systems as an example.
The world is moving toward a single key system for digital goods and services. This is true now for financial services (SSN). We wouldn't dream of using just one key for everything in the physical world. That's an interesting idea. I wonder if it was practical, would we?
There a many activities where we don't require identity from people. Jim mentions giving someone (who he didn't know) having someone approach him and ask for a hug on a bus in DC. "The only requirement I have is the absence of a bad smell. That's not an invitation..."
Knowing who people are, when flying, for example, doesn't make us more secure. The characteristic that matters is that the person sitting next to you on the plane is incapable of doing something to harm you and others. Will we require ID in malls, bus depots, parks? Will people be stopped as they walk down the street?
A national ID will make us less secure as individuals because it makes government and large corporations more powerful.
RealID won't make us more secure. Terrorist and criminal groups will beat this system using corruption and fraud. Illegal immigration will beat the path that more nefarious groups will follow.