It's just the same as gun registration.....really stopped the bad guys from getting guns didn't it? Lay out a scenerio where a national ID card could protect us from anything.
The technology to insert chips with encrypted information exists today. Modern codes are not computer breakable. The cards would also serve as passports. Various levels of businesses and/or government entities such as customs would have access to varying levels of coded information that could be deciphered with a simple pass through a reader. New identities could not be created. Existing cards could not be modified. Lost or stolen cards could be instantly invalidated, world wide. Visas for entry into the U.S. could require much more, verifiable information.
For the past half century I have been adamantly opposed to national ID cards for all of the reasons stated above in this thread but have been forced to reconsider by the reality of today. We have long existed in George Orwell's 1984 nightmare. Computer technology does not create the problem; it only facilitates evil government. Our job is to defend liberty and control government unrelated to technology.
As other posters have noted, we effectively are forced to carry "papers" today to function in our society. They are too easily created or altered. It is time to rethink the issue. Sadly, I believe the benefits of a national ID, today, outweighs the downside.
How much proof do you want? The proof would be in the pudding. In other words, until they are established there is no way to prove anything. But there are a lot of things the government could do to make them near counterfeit proof, depending on how much we're willing to give up.
For example: they could be entered in a central computer before they are even assigned to anyone and then tracked all the way to issuance. They could then set up check points, similiar to ATM machines, at public buildings, airports, sporting events, and anywhere where large numbers of people congregate. They could even set up roadway check points. They could likewise include identifying marks such as finger prints and/or video identification scanners. Depends on how far you want to go..
Any cards entering the system midway would then stick out like a sore thumb. I'm not sure I would want them to go that far, but I would be willing to think about it.
The way the system is today, the terrorists can probably get information on us but we can't get any on them.