Loads of these videos on youtube. This has become a phenomenon in the inner cities. From what I've seen, these guys can really ride, especially considering their lack of training. I've known a few guys over the year that could ride the back wheel like that, but they've been riding for years. Conducting this sort of activity on the streets is dangerous, but providing an alternative location to do their thing also presents liability for someone looking to do something good. Here's a video of 2 crazy guys I know. They're both absolute clowns on bikes, but they can always make it work. Both have done well in life from their riding expertise. Hopefully some of these kids riding on the streets will get noticed and find something passionate to do with their lives.