Interesting. I agree, of course, that you should ask as a matter of courtesy, but it will be interesting to see how the legal aspects of these activities evolve as more and more obvious recording is happening around us on a daily basis.
It seems to me that people are perfectly fine with being recorded as long as the recording is being done by a trusted authority. We see cameras all the time in banks, parking lots, street corners, airports, retail stores, etc., and nobody gives a damn. But as soon as the camera is in the hands of an individual who might post on youtube, the gloves come off.
The guy in this video was recording video mostly in a really aggressive way. I'd be more interested in seeing how people react when faced with cameras in the hands (or on the faces) of people with whom they're already interacting with naturally, i.e. during a retail transaction, personal conversation, etc. I'm not sure how anyone would go about experimenting with that, but it would be interesting to see something like this without the obvious deliberate intent to aggravate.