On a related note, does anyone know the logic that makes these naming rights so damn valuable? There has to be an advertising study or tennant that shows that repeating it over and over has some positive effect, but I've never been able to figure out why it's worth so many millions of dollars.
What strikes me is the cost of selling the name. The teams lose brand value. The Yankees will never sell naming rights to Yankee Stadium because it would lessen their own brand. Non-team name fields names can have brand power: note Fenway, Wrigley and, even, Camden Yards. You will not get that with corporate-purchased names because they will change when a new advertiser is found or the company is bought or merges with another.
I think this name-selling will go away as teams realize this. It will be like the multi-purpose, artificial-turf, cookie-cutter stadiums of the 60's and 70's. They seemed like a good idea at the time but were completely ridiculous a generation later.