I say it's a bad idea. I like my privacy, and I'm not rela big on being tracked, cataloged, and monitored.
Also, I have enough cards in my wallet already, I don't want anymore.
Anyone else forsee a future reminiscent of the USSR? Where you have to show your official documentation/IC card at every state line you drive across, every time you get on a plane, every time you buy something, etc?
I think that sucks.