ID checks in the US

I've noticed that I am asked for ID in the US much more often than in Australia - usually when checking into hotels or hostels, and quite often when paying with a credit card. The amusing aspect of this is, however, that every time I've been asked for ID, they have accepted my Victorian driver's licence without question (my passport is in my money belt, and I can't be bothered going through the effort of getting it out).

Now, I'd bet that none of these people have ever seen a Victorian licence before, and certainly wouldn't be able to tell a fake one from a genuine one. Most probably wouldn't even know where Victoria was, nor whether it was a jurisdiction that is allowed to issue licences at all. I could imagine them accepting an official-looking laminated piece of plastic with my photo and "City of Wangaratta Driver's Licence" written on it, too.