If ever there was an optimistic expression of the seductive power of the MMO, it's in the trial program. All game makers have to do is offer a way for existing subscribers to give a taste of their product to their friends, and these new players will fall head over heels into the pile of paying customers. It's a sound marketing strategy really; who knows better which kinds of people will be weak to the siren song of an MMO better than their friends, co-workers, and family members? In politics, they call this micro-targeting.
According to Cameron Sorden over at Random Battle, the thing that sets SWG's Buddy Program apart from the competition is that instead of offering incentives in the form of free playtime (as with the popular Tabula Rasa Recruit a Rookie program), they offer in-game rewards to players. By Sorden's logic, most gamers already consider their subscription fees a sunk cost, so the greatest incentive is something that will enhance their in-game experience. He takes it a step forward and suggests that rewarding players for recruiting whole networks of new players, would provide the greatest return to all parties involved. It's an interesting perspective, though personally I would probably stop short of the whole pyramid scheme idea.