Easyjet operates a priority boarding system called (predictably) Easy Boarding. You get on ahead of other people, and can therefore select your seat more easily (it's open seating on these budget airlines, which allows for costs to be minimized and a faster turn-around –passengers board quicker if they aren't tring to find a particular seat and making other people move in order to get to it).
As we flew down to Nice this week for an ASI awayday, Stelios – the airline's founder and major shareholder – happened to be on the plane. It was a full flight, and quite a few of those who boarded last could not find seats together. "You should have got Easy Boarding," Stelios told them cheerfully. "It's only £5."
Ah true: but what would happen if everyone took his advice. Then everyone would have Easy Boarding priority and the people at the end would still be at a loss. Then of course there would have to be Really Easy Boarding for another £5! Stelios would have raised the price by a fiver all round! But maybe that's why he's incredibly rich and I'm not. Ho hum.