I'm sure that's true for some small percentage of the population to try and one-up each other with dangerous acts. But the fact that they do it because it is illegal is very dubious. Where is the world of underground illegal cycling on freeways? Right, there is no culture of that because no one from the general populace is doing that for fun. The one-upping can only exist in a culture that is well established via some other means. For instance, search for "gravity biking" which is an incredibly dangerous sport that only exists in places with a big cycling culture. The legality of pot has nothing to do with daredevil behavior.