Ever since the airlines started to charge for checked baggage, I have preached that they have it backwards - they should be charging for carry-on. This would discourage the folks who believe that the carry-on rules apply to everyone but themselves [which unfortunately is most of the folks] and diminish the major cause of the great increase in the time that it takes to board a plane. The New York Times recently had an article about this problem and noted that there are some mathematical solutions to optimize the boarding sequence. Although it seems that everyone and their sibling now has "priority boarding status", it is clear that the carry-on barrage is the main contributor to the craziness.
Only one airline thus far has figured out that they should follow my recommendation. Spirit Airlines now charges $20 - $40 per carry-on bag, which is more than they charge for checked baggage [which I still believe should be free.] And as predicted, with less carry-on, the boarding times have dropped dramatically.