Nano video (updated)

When the iPod Nano came out with built-in video recorder, I thought it was a weird idea. Well, I was wrong, it's pretty cool, and the video quality is far better than we had a right to expect from a device so small it can get lost in a bag of candy.

David Pogue said in review that this device will make for a lot of spy-filming. I've no doubt he's right, but it made me think: is that even legal?
In private settings probably not. But in most countries it's legal to photograph anything you can see in a public place, so does that go for filming too?