NewUmpire, they already do the short spots in baseball. Usually when the catcher calls time and runs out to chat with the pitcher (now, here is where they should cut things off by limiting these). I also agree with the batters stepping out being a bigger time sink than throwing over. Limiting those two would make a big different in my opinion.
Also, anybody watch a College football game recently... Now, those are ridiculously long.... Good for TV, as with DVR, it doesn't take long to catch up with with commercials.... Again, ridiculous.