One of the most interesting aspects about the recent arrest of Henry Louis Gates Jr. was something that went completely unreported in the US, though I suspect it would have been the first thing on everyone's mind in Europe: why did the man's neighbor call the cops in the first place?
I imagine that most neighbors would know each other, and if you don't you can probably just walk over and see who the guy is -- at least in Europe. In the US, you might be afraid that the guy is going to have a gun and kill you.
Recently, Bob Dylan was arrested. He was standing in the rain in front of a home with a for-sale sign. The people inside the house did not view the man as a potential buyer (Dylan says he was indeed looking to buy the house), but rather as a crazy vagabond who was walking around in the rain. In the US, walkers are often treated with suspicion, and some suburbs do not have sidewalks at all, though there is a trend to have them retrofitted these days. If you simply want to take a walk in many parts of the US, people will assume that your car has broken down (in which case someone may stop and ask you if you need help) or that you cannot afford one and are destitute. Few people will assume that you are simply taking a walk.
It is unlikely that Bob Dylan would have been arrested under similar circumstances over here in Germany. I contend that the average German who notices a strange man standing out in the street looking at their house would probably not even think the man is especially strange. In fact, I am sure that things like this happen all the time; every time I go outside, there are all kinds of strange people looking at all sorts of things.
I haven't called the police yet, but it would be interesting to see if they would take me seriously at all. I wouldn't be surprised if they asked me, "Someone is standing out in the rain looking at your house, and you want us to come by?"