I dont know this person but I doubt he will get tired from banning. 20 bans should have taken the message already. Maybe is his 'stat of honour' ,like some people have ratings or bounty hunts... lol .
What about all stop bothering with him. yahoo has an effective ignore option. Just put him on ignore on every new id that he makes. HA's of the leagues he plays could send an email to the players as soon as a new id is spotted. DONT ban him but ignore him. Some people feed from attention. He will get bored.