Online poker WAS huge 10-15 years ago. For the website (the casino always wins) the money is in the haircut, not in cheating. Until the real casinos got most of online plays banned.
Anyhow, let's go back to the original topic of player backing players. What if the final 10 has a player who also backed 2 other players? That is a clear collusion, because the backer has a 30% chance of getting eventually some money compared to the others at the table. Once the backer realizes he is not going to make it he can lose his small stack to one of his backed players. Other funky plays are also possible...
Anyhow, let's go back to the original topic of player backing players. What if the final 10 has a player who also backed 2 other players? That is a clear collusion, because the backer has a 30% chance of getting eventually some money compared to the others at the table. Once the backer realizes he is not going to make it he can lose his small stack to one of his backed players. Other funky plays are also possible...