It seems as though there may be something primordial lurking within Farmville that generates such mass appeal. We slave away at desks, in cities, or at libraries if we're students, and deep down long to just tend to our flock or nurse some vegetables in our allotment. Crucially, we like to show people what we've grown and let them know how happy we are doing it. This is what Facebook had to say about the trend:

Facebook has provided a platform for developers to create a number of hugely popular applications, and it is no surprise that users are talking about them. Rather surprisingly, the recent trend has been in farming related apps. It seems that with Facebook users spending more and more time online and less in the field, they need to channel their primal urges to farm somehow, and farming apps fill this need. Since its emergence in June 2009, Farmville became the most talked-about application in status updates and now boasts over 72 million monthly active users.

Update: A few people pointed out that applications post status updates and they claimed that this was the cause of the incredible growth of these apps. However, our analysis includes only status updates made through the status update box, mobile devices, and Twitter, not those made by applications.