Excellent question Nickpicky and a great topic for discussion.
Personally I prefer “Fencing” as it gives everyone an incentive to promote the individual properties or brands that the casino group has. When they are combined it removes that incentive.
One key point from me though
If the player ventures to another property within the group via internal marketing by the casino the original affiliate SHOULD still receive credit. If not then you could have problems with cross promotion by the casino group poaching players (especially whales) from affiliates and thats obviously NOT a good thing.