Verification is a great way to keep the other players at the table honest. By this I mean that the player has the hand that they claimed to have had at the showdown and that they had a hand that they would have played in the same or similar way to that of which they did.
This simple rule prevents other players such as colluders and anglers from getting involved in pots with hands that they should not be involved with. For example, player A has AA and player B has 36o. Player A calls and lets player B raise, then player A reraises in order to get the most money in the pot.
Verification of the hands at showdown is easy and would help keep everybody honest if they know that they can be called out at any given time. Another good rule to implement is to make sure that players who have pot interaction to do so in a slow and obvious manner. Doing so will ensure that they are not taking money from the pot or using other sleight of hand methods to cheat at poker.