Almost none of the goods you can buy in this game serve any purpose except decoration. Creating an elaborate farm has more in common with posting a funny link on your Facebook profile than it does being a high level warrior. And if you hadn't noticed, people like to post crap on their Facebook profiles. It does not need to persuade anyone of anything, it is simply another set of things to broadcast about yourself on the internet.
That twinge of pride you feel at your gamerscore? That urge to post on Twitter what you're ticked about that day? That's Farmville. That's Warhol's prediction about 15 minutes of fame, but now Zynga is selling it one minute at a time to whoever will pay in time or money."
L.B. Jeffries introduces his recent Popmatters piece analyzing the appeals of Farmville, both commercial and gameplay-wise