L-Frame:
I can think of two reasons to vehemently oppose any form of national ID.
1. As a matter of principle. This is supossed to be a nation BY the people, FOR the people, not by the government, for the government. The question should be, why the h*ll SHOULD we submit to our government cataloguing us? Just because our SSN's are often used in this capacity (much to my dismay) is no reason to make it worse. It's like saying, "Gee, you're already wearing those handcuffs, why don't we just put a lo-jack on your ankle and a shock collar around your neck while we're at it. It'll be much more efficient that way."
And not to offend any LEO's out there on TFL, because I have tremendous admiration for you for doing a difficult and often thankless job, but I don't give a wombat s**t for the claim that a national ID will make things easier for the police. First of all, the only place that the police have it easy is a police state. Secondly, this will ultimately not be effictive for the same reason that gun control efforts are doomed to fail at reducing crime... criminals by definition do not adhere to the laws. Forgery, ID theft, fake ID's, oh boy would we be opening up a whole new market for this segment of The Black Market.
2. The "if you're not a criminal, what do you have to worry about?" argument won't work either. If we end up with a national ID system, you can pretty much garuantee that if you're not a criminal now, you will be at some point in the near future. We already have so many conflicting laws on the books that every one of us could probably be found guilty of something. Just look at our current tax code. If we get a national ID, look for this sort of thing to progress. Then we can all look forward to more no-knock raids, blank warrants, asset forfeitures, intimidation, and brutalization.
To sum up, all national identification measures represent another step in the ongoing erosion of our liberties. Where do we draw the line?