I've had a national ID card now since 2007 when I got my second citizenship here in Europe. I think it's great, but I do understand why people are hesitant about it. But as pointed out before, if you have a credit card, a drivers license, a bank account, etc, then the Feds have everything they need on you anyway, so why not simply things for the government to help reduce spending.
Here's why I like it - it has a chip in it so with an ID card reader attached to my computer I can, from my computer anywhere in the world: vote in local and national elections, I can digitally sign any legal document sent to me via email (using DigiDoc), I can purchase tickets on public transportation (the train attendant just reads my card to see I paid), I can pay and/or amend my taxes online, I bank more securely using it in combination with my user name and passwords plus loads of other things. Basically it's my official ID online and I can do virtually anything from my computer with it that would normally require me to be somewhere in person and sign a document. In a way, it's gives me much more freedom, which is opposite of what you might think it does.
Is there potential for abuse. I presume there is with anything, but don't know of any particular problems with the national ID. They've been around a long time and in use in most modern countries, so they are well aware of any problems.
Speaking from a European point of view, personal privacy and personal information is very restricted here in the EU and privacy laws are much more stringent than in the U.S. (since the Patriot Act for sure) so there are tough laws in place as to what information can be stored and retained by government agencies. Not to say that abuse doesn't happen, but it wouldn't be any worse than what happens in the U.S. today from what I can tell.
Here's what I don't like about my national ID: My drivers license isn't incorporated into it. I wish they would do that so I only have one important card to carry around.
I've heard the argument that America is big and diverse so it would be hard to implement, but almost all 27 EU countries so far as I know have one and that population is more than the US with an even more diverse illegal population.