"Farmville is not a good game. While Caillois tells us that games offer a break from responsibility and routine, Farmville is defined by responsibility and routine. Users advance through the game by harvesting crops at scheduled intervals; if you plant a field of pumpkins at noon, for example, you must return to harvest at eight o’clock that evening or risk losing the crop. Each pumpkin costs thirty coins and occupies one square of your farm, so if you own a fourteen by fourteen farm a field of pumpkins costs nearly six thousand coins to plant. Planting requires the user to click on each square three times: once to harvest the previous crop, once to re-plow the square of land, and once to plant the new seeds. This means that a fourteen by fourteen plot of land—which is relatively small for Farmville—takes almost six hundred mouse-clicks to farm, and obligates you to return in a few hours to do it again. This doesn’t sound like much fun, Mr. Caillois. Why would anyone do this?

...

The secret to Farmville’s popularity is neither gameplay nor aesthetics. Farmville is popular because in entangles users in a web of social obligations. When users log into Facebook, they are reminded that their neighbors have sent them gifts, posted bonuses on their walls, and helped with each others’ farms. In turn, they are obligated to return the courtesies. As the French sociologist Marcel Mauss tells us, gifts are never free: they bind the giver and receiver in a loop of reciprocity. It is rude to refuse a gift, and ruder still to not return the kindness.[11] We play Farmville, then, because we are trying to be good to one another. We play Farmville because we are polite, cultivated people."

Quoted from Media Commons

I don't play Farmville, or any game of the same genre (Restaurant City, Hotel City, Social City, Gangster City, City in a City, etc... okay I made the last one up), but the whole idea just shouts PONZI SCHEME.