The story behind the story is that someone asked Arison why the greedy owners continue to lockout the players when all the players want to do is getting back to playing ball.
Arison responded with "you have the wrong owner" and then deleted the tweet. Other owners went to Stern and lobbied for an especially large fine because the tweet publicly showed for the first time that there was a split in the owners regarding their needs and demands.
Other owners had been fined $100,000 for their comments regarding the lockout thus far but none showed any lack of solidarity on the owners side. This did so Stern went along with the group of owners that complained to him and levied the fine of %500,000.
Can't help but think this shows that there are probably a group of small market owners that are driving this push for every possible concession they can get out of the players and are the ones driving the hard ball negotiating tactics we have seen. My guess is teams like LA, NY, Miami, Chicago, Dallas, Orlando and Boston would settle right now to begin the season with the concessions received thus far as they are all contenders looking to get the season going and making money.