Dom,
The affiliates that are doing rake back are simply taking a big percentage of their monthly earnings (in most cases ~ 80%), and giving that back to the players that signed up through them. The players are getting a percentage of their rake back.
It was the affiliates whom came to the poker room and asked if they could give a percentage of their earnings back to retain their customers. We try to accommodate as many special request for affiliates as possible, because you are part of our marketing team. If you have an idea that will help you bring in customers that is within our abilities to help, we will try to do so.
In addition, 49er Casino and 3 Diamonds offer 10% back on net losses to players. This is in an effort to help retain customers, because in the long run, retention is the key.
If I can answer any more questions, please let me know.
Kind Regards,