You know you're really late to the party when you learn about a new trend in youth culture from the Times' Sunday Styles section. Sadly, that's what happened this weekend when I read Guy Trebay's article on "jerking," a new dance craze that's apparently burst out of Los Angeles via the internet. On the upside, the new knowledge answered a question I'd been asking my television machine for the past few weeks. This was: What is that spastic karate-chop shit the crazy-haired girl in those "All You Need is Love" Blackberry commercial is practicing in front of her bedroom mirror? It seems strangely codified; she films others doing it, then tries really hard to perfect her own version. You feel embarrassed for her when you see it. (I hope she got a paid a lot for that commercial.) But then we're asked to believe she wins the respect of her crew and their rivals after executing perfectly in a street dance-off competition. (The theme of the commercial seems to be: You can do anything if you really try your best. Climb a mountain, make clothes, do ballet, whatever.) READ MORE