It's true that 'word of mouth' marketing can only take you so far, but in the case of cRPG it still has a long way to go before it dries up.
Is there any way to motivate players to get their friends playing? I've gotten at least five of my friends to start playing since I was introduced to the mod, and a focus on this type of 'marketing' could help a lot.
What I'm talking about is some sort of referral program. Allow current players to 'refer' their friends and get some sort of benefit for doing so. This could be gold, experience, or even something as valuable as a loom point. Another option (that only some would probably care about) is a special in-game or forum title for referring certain benchmark numbers of new players.
New players would simply have to say who referred them. Rewards could be given when the referred player activates an account on a new CD key, or delayed until the new player reaches a certain level (i.e. 30 or 31; by then I think we'll have them hooked).
Is this viable? It would take work to set up, but could definitely help get the game out there.