If you try to book a normal coach ticket these days--either directly through an airline or through a discount site like Orbitz--you'll find there are a lot fewer seat assignment options ahead of time. That's because airlines, hoping to squeeze every last cent out of their passengers, have started setting aside huge blocs of seats as Coach "Preferred," "Select," or "Choice" options that you either have to pay for, or be a loyalty program gold member.
The more annoying thing, though, is that these seats are no different from normal coach seats. They're just on the aisle, or closer to the front of the plane! Is that worth paying $50 extra for? Based on a recent experience in one of them, I think not!
Find out all I have to say here at my Jaunted article: http://www.jaunted.com/story/2009/6/30/134118/624/travel/There%27s+Not+Much+Of+A+Selection+In+Coach+Thanks+to+Those+%27Preferred+Seats%27