To my mind, this highlights the political difficulty that the government will face in dealing with the debt crisis. If they don't slaughter certain "sacred cows" (as the Independent's source calls the ID card programme), then they're open to the charge that they're not taking the problem seriously enough. But if they do, then some of New Labour's more totemic policies will have to be flung on the scrap heap, while the opposition benches chant "we told you so". As the recent "hoo-ha" over IHT showed, the Tories also face this problem - but it's diminished by the fact that they haven't been in power for the past 12 years, and their policy ideas are naturally more up in the air.
On ID cards, my gut feeling is that Brown will stick with them. His instinctive urge to spend, spend, spend doesn't suggest that he'll drop expensive programmes for the sake of the public finances. Especially as he can promise jam today, and leave it to the Tories to serve gruel tomorrow.