I will support baby's idea, but think they should manage it better!
I believe they got the idea from FCA - who were making a good wodge of cash.
The procedure at FCA is very well managed, and is a good money spinner. They have been doing it for years.
People need to understand the difference between Emergency exit/legroom seats, and standard exit/ABP seats.
Not all exit seats have additional legroom - some are just isle seats that are situated near a main exit. These have to be occupied by a fully ABP person incase the crew are incapacitated during an emergancy landing.
HOWEVER, Overwing exit seats can offer generous legroom to people that really need it. Putting a pre-pay system in place such as FCA's example allows tall passengers to upgrade to extra legroom seating at time of booking, giving them the comfort of knowing they are not going to have their knees around their chin for the family holiday to Corfu! The pre-booking procedure (as already mentioned) is governed by very stringent questioning, which if the passengers are willing to lie to will find themselves moved without refund!
Whatever seats are left at check-in (if-any) can be sold to the remaining passengers who are usually eager to get at them.
As I mentioned above FCA's policy has both customer service and money at the forefront, where as baby has just money. If they could implement some form of pre-booking service they will find it a lot easier to handle!
Criticise away Chaps!!
