I think it does depend on the situation. If you bet that you can do a special "thing," that you have technique or practice or whatever at, and someone bets against you, fine.
If you bet on a puzzle where it's clear there's a trick and the trick has to be discovered but all of the necessary tools and clues are available, fine.
If you make a bet where you have tricked someone with words- your description of what you could/ would do, for example, I think you're walking on some dangerous ground.
Others might also argue that the standard is to never bet a man his own trick, so fair game.