Apple’s App Store is currently experiencing a plague of fart applications. Last week, I detailed one day in which at least 14 new fart apps were accepted into the store. And now, just in a quick search, it looks like there are about 50 apps all dedicated to making fart noises on your iPhone or iPod touch. Classy, I know, but why are there so many?

Because apparently there’s big money in fart apps — nearly $10,000 a day for the most popular ones.

Developer InfoMedia (Joel Comm), which makes iFart Mobile [iTunes link], has been releasing download statistics for the app each day since it launched. The $0.99 app has been in the top 100 paid apps every day since its launch, and has seen great growth. In fact, yesterday it hit the number one overall position with over 13,000 downloads. MacRumors ran the numbers, factoring out the 30 percent cut Apple takes from each sale, and determined that, yesterday alone, iFart Mobile made its developers $9,198.

Certainly, a part of this onslaught of fart apps is that Apple, which had previously rejected all crude apps, changed its policy to let them in. But now that they glimpse the potential for big business in fart apps, expect even more to come.

Of course, not all fart apps are going to make it to the number one paid app position, but a number of them are selling well. Personally, I prefer Pull My Finger [iTunes link], but it’s hard to argue with iFart Mobile’s icon, which simply reads “Best Fart App!”

Update: Incredibly, the days following this story saw the app’s popularity explode even more. Christmas Day alone saw nearly 40,000 downloads of the app, netting the company nearly $30,000!