I dunno how many actually believed Proteus would pay up or not(Personally I would trust any deal made over the internet about as much as I'd trust the most politicians, which is to say not at all).
But that isn't really relevant anyway, it doesn't change the fact that he was very vocal and public about making that bet and later chickened out when he lost. And for that he deserves to be taunted and scorned ever so often.