Is this legal and to what degree is it?

A buddy showed me a video of this guy walking around video taping in public. No specific reason or anything.

Here is link to his videos on youtube

http://www.youtube.com/user/SurveillantCameraMan?feature=watch

Is this legal or not? Or exactly what can he do and can’t do in terms of recording/video taping?

Also try not to get caught up in “principle” I mostly want to know strictly the laws of it. Although I was surprised at quickly people escalated into threats and force. Few times people chased or put hands on him.

Pretty funny though and a little sad to think people are so insecure in many ways…. How would you react to something like this?

Thanks!