I think Jordan, is in the top (or bottom) 10, but he has a way to go to match Isiah Thomas, who bought the CBA, then mismanaged it into bankruptcy. You've got to admit that's worse than drafting Kwame Brown ... killing an entire league. Then he followed that classic screwup with his tenure as GM of the NY Knicks, where he not only ran the franchise into the ground, but also tied them up with so many long-term contracts that they are still trying to dig themselves out. As a cherry on top of that foul sundae, he was nailed for sexual harrassment while running the Knicks, costing the team $11.5 million.
I'd also rank Michael behind Donald Sterling, who has turned the LA Clippers into a by-word for mediocrity in his 30-plus years owning the team. On top of that, Sterling actually financed Jerry Buss' purchase of the Lakers -- installing the owner of his biggest rival and one of the most succesful sports franchises for that era.
I'll have to think about baseball owners for a while -- there have been a lot of bad ones. The NFL is such a league-run organization that it's hard to be too terrible. Guys like Al Davis and George Stiennbrenner and Mark Cuban my be obnoxious at times and they may make some bad decisions, but they at least try very hard to win and have enjoyed success at times. I don't think they belong on this list.