The biggest problem with the ID cards being proposed by the UK government is trust, and here is a great example of it being misplaced ...
The public have been trained to trust the "Chip and PIN" (C&P) system of card payment authorisation. The banks in the UK have sold the idea that C&P is totally safe and thus any misuse of a card and it's PIN is the responsibility of the card holder. Under a deluge of relentless marketing the public have indeed come to trust C&P. Of course the public should not have been so trusting, as is now clear.
If you have time, do watch the BBC Newsnight video on this subject. (BTW, Jane Badger is not a relative of mine, as far as I know).
... For every mention in the video of the term "Chip & PIN" replace the term "National Identity Card", and you have a flash forward to a sampling of the kinds of identity theft problems that any national ID card will cause.
It is not the technological weakness of such systems that cause the big problems, it's the trust we the public place in them.
And as an aside, I had a C&P transaction fail just last week in London. I immediately went to my bank and said I wanted a note on my file that something weird had happened at the particular store. The response from the bank staff member was initially that I should not worry because C&P is perfectly secure (in fact she was rather annoyed that I was bothering her with such a 'trivial' matter).
Trust them not.