Fred, The You Tube sequence of Bruce Gilden simply proves once again that there are a lot more horses asses in the world than horses. Who says Bruce is a "great Magnum photographer?" Bruce? If he's an example of a "great"
Magnum photographer then Magnum has gone pretty far downhill since Capa and his buddies started it.This is the kind of guy who turns people against street photography. He's like the bikers who roar around with extra loud mufflers and then can't understand why the city comes up with a noise ordinance.
Your guy with the battleship-gun lens is another guy who proves the horse rule. You simply don't go into a place you're not familiar with and start pointing that kind of lens at people around you. There are
places where you can do that. As I pointed out in another thread, St. George street in St. Augustine, Florida is one of those places. So is Disney's Epcot, here in Florida. On Sunday I went to an art fair where you could do that. But to do it you have to be in a place where a large proportion of the people around you are carrying cameras. In that kind of place, people don't really think you're shooting a picture of them. They think you're shooting something behind them. If you're not in that kind of environment and you want to do street shooting you're much better off with something like a Leica or an Olympus E-P1 -- with the strap wrapped around your wrist and the camera in your hand, not around your neck.
As far as the rest of your question is concerned I can only tell you what the situation is in the United States, and even that varies slightly from state to state. Instead of trying to summarize it, here's a reference to a really good summary by an attorney who's also a photographer: http://www.krages.com/phoright.htm
Do I ask for model releases? Only if I think I might want to use a picture for advertising or sell it for that purpose. As long as I sell prints as art works or use the pictures for journalistic purposes I don't need a model release. On the other hand, I have to be careful to avoid making someone look ridiculous or mis-represent him in an invidious way. The other catch is "right of publicity." Right of publicity is defined as "an individual's right to control and profit from the commercial use of his/her name, likeness and persona." In most states it only applies to famous people. A movie star, for instance, could sue me on a right of publicity complaint if I tried to make money by selling a picture of her. But I still have the right to photograph
her as long as I'm in a public place and she's not in a place like, say, a restroom, where she does
have an expectation of privacy.
I've said it before and I'll say it again: if you look at the pictures of people on my web you'll realize there are very few instances where the person was aware I shot the picture. I think that anyone who does street photography regularly can say the same thing. It's just not that hard to remain inconspicuous while you shoot pictures -- once you learn how. But, of course, there's always the Bruce Gilden type around, detached from his horse.