UBC Engineering students used to put a Volkswagon Bug up on top of the Lion's Gate Bridge about once a year. They don't seem to do that sort of thing much anymore. The thing was, that the Students always came up with their own car, so nobody was suffered to wait for their car to be taken down. The students treated it as an engineering problem to get the vehicle up there. Basically, they took the car to pieces and put it back together in place atop the bridge. I don't remember anyone ever getting hurt at this.
Tipping over the Smart Cars is another matter. Someone's property is being damaged and that is irresponsible, regardless how funny it seems.