If you had to guess what the most popular Facebook app on Facebook is, chances are you’re not thinking that it has anything to do with fruits, vegetables and cows. But you’d be very wrong. What is the most popular app on Facebook? FarmVille.

As the name suggests, FarmVille is a game that gives users the ability to “grow delicious fruits and vegetables and raise adorable animals” on their own virtual farms. With nearly 35m active monthly users and 12m active daily users, FarmVille has just about grown itself into the most popular Facebook application ever. When FarmVille surpasses 35,554,755 active monthly users, it will surpass the record set by the How Well Do You Know Me? application.

Even more remarkable: farming is arguably the most popular pastime when it comes to Facebook applications. According to AllFacebook, “there are now over 72 million farmers on Facebook across the top farming
“. And while FarmVille is the leader of the pack, other farming applications are growing like corn: Country Story, for instance, now has over 4m active monthly users, up from 1.4m just a couple of weeks ago.

Farming is big business in the real world and clearly it’s clearly big business in the highly-competitive market for Facebook apps. FarmVille is the prize hog of Zynga, the largest Facebook app developer. Its apps collectively have just over 100m active monthly users, meaning farming makes up nearly 35% of its Facebook empire. The second largest Facebook app developer, Playfish, is the creator of Country Story. So where does the money come in? The cash cow (no pun intended) for many Facebook apps is virtual goods and that’s the case here. While FarmVille is free to play, users can enhance the experience by buying virtual goods.

Personally, the success of virtual farming on Facebook brings a smile to my face. It’s nice to see that something wholesome can exist on social networks that are otherwise commonly associated with various bad behaviors, including exhibitionism. What’s also particularly fascinating to me is that in the developed world, the number of real farmers has decreased significantly over the years thanks to increased efficiency and farming technologies. Many people think nothing of where their food comes from and will never meet a person who produces it.

Recently, legendary investor Jim Rogers predicted that we’ll see farmers, not investment bankers, buying Lamborghinis in the near future. If that’s the case, Facebook farmers willing to make the transition just might find that playing games on Facebook was a profitable hobby.

Photo credit: sabrina.dent via Flickr.