Trying to understand facebook games

Char: So, what's that Farmville game you play in Facebook?
Jeff: You build a farm, people give you stuff, and you give them stuff. It's fun, you trade sheep, cows, banana trees, stuff like that.
Char: So why do I keep getting requests?
Jeff: It's set up so that the more people you get on, the more stuff you get.
Char: Ah, ok, like banana trees.
Jeff: The games encourage it, because the more people you get to hit the app, the more ad space they can sell.
Char: Ok, I get why the applications want you to spam all of your friends for stuff. But what's in it for you?
Jeff: People give me banana trees.

Well duh! It's all about the banana trees. NOW I get it. :-D

(And while generally all of the facebook game status crap annoys me, I laugh every time I see the "lost cow" one...)