PlayStation 3 causing riots

Two people were arrested after a crowd waiting to buy Sony's PlayStation 3 rushed an electronics store, trampling people in the parking lot of a Fresno shopping center, police said. Police declared the crowd of several hundred people an unlawful assembly about 10 p.m. Thursday and threatened to use Tasers on the die-hard gamers, some of whom had camped out since Tuesday hoping to buy one of the 34 consoles for sale at Best Buy. More at FUK.CO.UK. Check the YouTube video as well.
My question is: why didn't this happen with the Wii launch? Because they had more than 34 units? Or because there were families with children in the crowds? Or because...