The ID cards scheme is likely to be a disaster on financial and systems-integration grounds, but even if it worked as intended -- I admit that I am inferring its intention from clues left in the Bill, consultation documents and various utterances of David Blunkett and ministerial cronies, since its purpose is as yet unexplained -- I would oppose it.
At root, I don't think that it's the government's business to tell me who I am.[my emphasis - cm] The government are our servants, not our masters, and we oughtn't to let them forget that. Just as -- see Saki stories passim -- the Edwardian upper classes assigned names of convenience to their servants, David Blunkett intends to assign names of convenience to us. There's no good reason to let him do that, and I don't see why we should.
In more detail: the conceit of the ID cards scheme is that each person should have only one identity; that that identity is given them by the state and recorded authoritatively in the National Identity Register; that each person must notify the state of any changes to it, and such changes will be accepted at the discretion of the government; and that that failure to comply as prescribed by the law will result in various and novel penalties intended to result in compliance with these rules.
That's pretty much my opinion, in a nutshell. I recommend that you read his whole esay though: it makes most of the salient points, I think. As he puts it, this is a really important issue. Think about it, don't let apathy guide us into a database state...