I am pleased that an issue I raised several years ago (to much criticism) - "backstopping" - is now generally recognized as business as usual on the tour. The correct remedy under the rules today would be for both players to be disqualified, as it is obvious that they are agreeing to help each other, if only tacitly. Of course, this never happens.
I made a suggestion then for a rules change, and I will repeat it here. If player A's ball is within 5 feet of the hole, and player B's ball is withing ten yards of the green, Player A must mark his ball. If he does not, and if Player B's ball strikes Player A's ball thereafter, then Player A will be penalized one stroke. That will put an end to "backstopping." And no, players will not measure distances before deciding whether to mark the ball on the green. If that happens and the ball is left near the hole, the only explanation will be collusion. And again, no, this will not cause a material slow down in play.