[Guillermo]

Sometimes buying 2 coach seats can be cheaper than a 1st class seat.

[mamelukesabre]

What good is it to make a large person buy two seats? It's not like their going to sit on the crack between the two seats. And the seatbelts don't go in the middle either, or the fold down tray, or the head rest, and you can't recline two seats at the same time very well. First class probably also gives you more leg room too, I don't know for sure since I've never flown first class. But most people that large could also use the added leg room.