The game is stepping outside the bounds set by other facebook apps with the new legion system, but it still needs a way to propagate itself.

My best idea is for a personal referral system where it rewards existing players for inviting new players. People that aren't playing already. GP seems to be the obvious reward. Dan has already been stingy with the 'awesome points' compared to other apps, so it is still a monumental reward to anyone playing without paying, which would be the vast majority. This seems like a way for him to take the moral high road and still be ultimately successful. The game speaking for itself to a NEW base of players seems like the best idea to me considering how much I like it.

There has to be other ways, but it would have to work in new ways considering the new system and that most of our facebook friends probably don't already play, and facebook limits invites on apps to 4 a day.

If the high road doesn't work there might have to be a way to implement having GL friends providing benefits in new ways.

My guess is that Dan, in his omniscience, has already put some thought behind this question, but there have to be answers besides my own.

referal-links only generate mass spam to unwanted people, networks and forums.

Well WE wouldn't be getting the spam

There will probably have to be spam. Success of the invite should be what determines the reward. People might actually get new players in the game instead of just using a mass-add list like other apps. Even requiring sharing of stuff for missions won't really get new players. I don't really see why the conventional means of getting people to play a game actually work besides someone saying "Why this 12434st notification about farmville/maffia wars?" surely it must be awesome if everyone is already playing it. I don't really know if a grassroots approach would actually work, but it would be much less deplorable.

Spam is spam, doesnt change because you change the label to "Rolls Royce"