There was a long discussion of this in this thread over at the WN board recently. The problems I see on all airlines are:

1) No enforcement of the one bag and one personal item limit (i.e., people with three or four bags); and
2) No enforcement of baggage size limits, I've been seeing more and more of those large wheeled garment bags which barely fit in the overhead and basically take up as much room as two roll-aboards that are the proper size and will fit in with wheels in/out.