May I see your national ID... I mean passport card?

I didn't hear about it in the mainstream media. Even my usual online libertarian news sources didn't report on it. I wouldn't have noticed it at all if I wasn't renewing my passport... and was asked if I'd like a passport card as well.
It looks like a driver's license and acts like a passport (but only in North America and the Caribbean.) According to our dear Big Brother, it's sole purpose is to simplify the lives of people who frequently drive back and forth across our immediate borders. Technically.
Now I realize this card will simplify Mexican and Canadian border crossings. And I realize you can't even enter a federal building nowadays without showing ID. But I have a feeling the purpose of passport cards is far more insiduous. It may be a stretch, but this whole situation immediately made me think of Soviet Union era internal passports.
In the good ol' days, I've been told, a "verbal declaration of citizenship" was enough to allow you to cross into Canada. Now you need a passport. And after some initial protest, people buckled down and are now showing passports twice a day at the Canadian border. Would it be paranoid to suggest that people would comply if the passport card became a mandatory, nationwide form of ID? Coded with all kinds of biometric goodies? Indispensable to get a job or conduct any kind of business (need I remind you that Social Security cards once read Not for Identification ?)
The passport card in its present form seems fairly harmless (unless you're concerned about RFID chips...) But if people get used to it, it could pave the way for far more serious government incursions on personal liberties. At the very least it deserves wider media coverage (and a nationwide debate beyond the confines of our meetings in Huntsman G86 twice a month!)