Of course, the obvious solution would be to pack less
I travel alone with my 4 yo frequently - and have a hard time trying to carry around alot of luggage AND a sleeping 50 lb. 4 yo (Always happens when I least want it to...) so have become a master at packing light. Last trip - we had a grand total of 29 lbs. between the 2 of us....
I find the biggest helps are to find lighter suitcases (or duffles) as some of the big ones can easily weigh15 lbs by themselves! (Thats 30% of your weight limit for pete's sake!) and to limit the number of shoes that you take (Okay - i've got closets full of them too - but they weigh a ton (Big feet

) so I now try to find pairs that do double duty - no pair goes that can only be worn with one outfit, etc.
As far as to why the airlines are imposing this weight limit - it's because they are broke (except for SW) and are trying to save a few dollars - not only on fuel costs, but on health insurance for their employees, and disability insurance/workman's comp as well (that prob. costs them a lot more than a few lbs. worth of fuel)--because back injuries are the leading cause of injury at work and can often injure them for life.....
Personnally - I believe the over-weight charge is much more fair than their $100 reservation-change fee- that only takes someone a few clicks of a computer to do - and I don't see that costing them much money at all....
Jill (A SW flyer when at all possible)