When/If the people who are wanting to decrease magazine capacities realize how quickly you can load a new magazine into your firearm, could they conceivably have a case on limiting the number of magazines you can legally carry or limit the total number of rounds you can carry.
Perfect example of a quick reload
http://youtu.be/Ls4Uq1aCiTA
http://www.youtube.com/watch?v=nM8nwZjaf1Y
Anyone see Jerry Miculek reload his revolver? Man that's fast.