Since the cost of pre-booking a seat is Euros 5.99 (£4.26) it is not exactly catastrophic. There is a larger issue which appears to have been missed. This being that pre-booking allows the passenger to book a window/aisle or whatever. Those that don't pre-book will end up crammed into a middle seat. By the way, British Airways does exactly the same with its short haul carry-on bag offering. Pay up to reserve a seat or get randomly allocated.