There are many news stories about the cost (said to be $3 million for 30 seconds this year) as well as the advertisers who are in or out. Last Friday, the online New York Times used an interactive timeline beginning in 1984 to show the advertisers and types of commercials each year.
I made a graph out of the percentage of spots the NYT said employed humor in each of the years. It shows growth in the "theory of liking" as an approach to creating advertising. Everyone wants to be liked, and effective humor can deliver attention, liking and memorability.
GE is preparing a Super Sunday commercial this year. It features a "spokes-scarecrow" for GE's eco-imagination campaign. I'd watch for this one as an effective use of humor.