If you can keep those concepts of play and competition, the behaviors are somewhat addictive. You can be addicted to fantasy sports just like you can be addicted to on-line betting - and I think there are probably several people out there who are like that.
Fantasy sports are a leisure pursuit that is akin to play - and we know really well that play is a very intense, spontaneous, frivolous activity, and that if you can sustain it, you get very dedicated people in it.