The number one selling iPhone Application last month was iFart. The modern day whoopy cushion, it allows its childish owner to select from a variety of sounds, set a timer and then prank an unsuspecting victim with the most humerous sound known to man (no I’m not being sexist, men do find this a lot more funny than women).

By my rough calculations, to be the number one downloaded iPhone Application worldwide, would require you to sell about 250,000 versions per month (although I can’t find the exact number). At 99c per download the iFart Application would gross its creator (who could very well be a 14 year old) close to $250,000 per month!

Now considering that this App might have taken all of a few days to create and Apples cut is only 20%, that’s not a bad ROI!

iPhone applications are big business. Techcrunch projects that a BILLION downloads of iPhone Apps could happen in the first 12 months of the App Store being open. That would make it as big of a success as iTunes.

The difference is that iTunes music store has a library of 10Million songs however the App Store has just “10,000 Apps and Counting”. That’s a lot of cash to go around.

The californian gold rush of 2009 might just be finding silly little ways to entertain and delight the 15M+ iPhone users worldwide. So, if you hear your 14 year old making terrible sounds in their bedroom, fingers crossed they are recording it.