"perhaps indicative of the operator's general business practices, which include bribing existing customers to recommend it to friends and family."
I guess you are not a fan of giffgaff.
Many companies offer recommendation bonuses. They are not bribes. Initially, with GG, the whole "payback" (rewards for recruiting new members or helping out those with problems) were a way to reduce support and advertising costs by having the customers do it for them. With recommendations/recruitment this is fairly common practice, and to call them bribes is inflamatory at best.