mlb.com (along with Avis, Subway, and Days Inn) are sponsoring a two-person, 50 day road trip all over the country to all 30 stadiums. Right now, they're on day 37 or 38 - anyone who is remotely interested in such a trip is drooling when they read about it, I'm sure.
As for whether UA would sponsor something like that - I don't know. Worst they can do is say "no," right? ;-)
Mike