Legal rights, charity and co-branded events

Michael SanGiacomo's look at the new charity raising funds for Cleveland's Superman celebration includes the following paragraph:

In any event, we can go through with a bunch of events this year, but the big Superman celebration at the Rock and Roll Hall of Fame had to be killed because there was not enough time to get all the necessary approvals from DC and Warner Brothers.

Recall the l'affaire Iron Man from a couple days ago, in which Marvel objected to an uncleared cross-promotional pre-screening. I'm rather impressed that the Cleveland organizers thought about the rights issue; many groups simply go forward without taking that into account. Sometimes it goes unnoticed without incident, but all too often it leads to headaches that could have been avoided.