Have a look here (section 8) for legality in Europe. The ones that ban them quote data protection law, which is probably correct if you take it that far, misuse of dashcam footage has already surfaced on YT so sooner or later it'll get raised in the courts then we'll see which way the courts decide over here. That's also why you can't get Google Streetview in most of Germany (which is a real pain when you are trying to look into somewhere for use with a wheelchair - hills, cobbles, etc!).
Dashcam - Wikipedia