Big Tone, who some of you met at the weekend, regularly buys himself two seats. Totally understand if he'd only bought one seat - because that's simply not fair on the passenger next to him who has part of the seat they paid for stolen by his largess.
Tony's biggest problem though, is a trend of economy armrests not to go fully back. On VS and EasyJet, he tells me, although both airlines were happy to sell him two seats as a passenger 'of size', they were unusable as such. Flights taken with the armrest pushed back as far as it will go, but digging in his shoulder blade.
He also has a gripe with the PE seats. Whilst they're advertised with extra width, that all seems to be at the seat pan area, but the armrests overlap and cut into him, making a PE seat worse than an Economy seat with the armrest up.
Perhaps they just need an extra-wide economy seat section, available for a supplement in the same way extra legroom is?