Maybe I (and others) haven't expressed myself clearly, or maybe you just got the wrong idea. (Or then again, maybe I misunderstood what YOU meant.)
I won't talk about what other people meant, but when I said there would be biometrics involved, I meant that TO USE the card, one would need to get their hand/eye/butt/whatever scanned. If you bother to do that, then, like Bruce said, there would likely be the best security possible. Also, the card wouldn't hold the info itself. That would be stupid. It would simply be a card that says to the card reader "ok, go access Database 8432984239b if this guy scans the right hand/eye/butt/whatever". Not unlike your bank card, (the magnetic strip tells the ATM to access your account, it doesn't contain your actual account info) but with higher security levels.
I'd personally say do away with the card, just install readers that access the proper information depending on what you're trying to do. If you want to buy something, the reader scans you, accesses your bank account, and takes out the proper amount of money. If you want to buy a weapon, it scans you, searches the police database to make sure you're not a dangerous criminal, and tells the dealer "this guy is allowed to buy an AK-47."
With proper security, there would not be any problem. And those who believe Big Brother would suddenly spring up, well, like Mr Cop said, wake up and smell the poutine. Big Brother is already out there.