Chris,
It takes a conspiratorial mind to believe that collusion is Tour-wide, but the only way that you could ever prove that a group of two, three, or four players was doing it, and DQ'ing them for it, is if the referee were to interject him/herself into the situation, as illustrated below.
22/7 Ball Assisting Fellow-Competitor on Putting Green; Procedure for Referee If Competitor Does Not Lift Ball
Q.In stroke play, a competitor's ball is in a position to assist the play of a fellow-competitor and the competitor is in a position to lift the ball under Rule 22-1 without delaying the fellow-competitor's play. However, the competitor does not take any action to invoke the Rule. Would a referee be justified in intervening and requesting the competitor to invoke the Rule to protect himself and the rest of the field?
A.Yes. If the competitor were to object, there would be strong evidence of an agreement not to lift the ball for the purpose of assisting the fellow-competitor in breach of Rule 22-1. The referee would be justified in so advising the competitors involved and warning that failure to lift the ball would result in disqualification under Rule 22-1.