Did you get an official reason for the denial, or was it simply denied?
I ask because in light of your comment quoted above it seems unlikely that Apple would deny your app due to its content.
Are you sure it wasn't a licensing issue?
I'm sure. The denial email specifically stated that my app violated this clause in the iPhone Developer SDK Agreement:
Applications must not contain any obscene, pornographic, offensive or defamatory content or materials of any kind (text, graphics, images, photographs, etc.), or other content or materials that in Apple's reasonable judgement may be found objectionable by iPhone or iPod touch users.
The decision is final. I offered to rename the application and remove any fart sounds that were "too offensive" by sending an email to
sjobs@apple.com and the reply said the decision was final.
The fat lady sang, nothing else I can do. I don't really want to cause a "stink" about it.

I just think its kinda sill that it was denied given so much more questionable content in the iTunes Store and wanted to get opinions of how people felt regarding it was denied. I also want to warn others that fart sounds will not be tolerated before they spend time working on a fart machine. My app is not the only fart machine that has been denied.
Who knows, maybe in some country fart sounds are the equivalent of to saying the mother of all curse words. How sad, I was going to add the timer for pranks in the next version and possible "belches" in a later version.
I kind of wonder if the larger concern is not the fart sounds, but the fact that I know this application would have become popular and Apple doesn't want the iPhone to be known as a $400 fart machine. I also wonder if the testers were having too much fun with it and they became worried that it might cause mass productivity loss in corporations. I know after I coded it, I played fart sounds for days and it's still not old to me, immature yeah, but I'll live a lot longer than those who cannot laugh at a fart.
I worked at one location in the past were it was very common to bring up online fart machines on your computer and rattle one off when the office became way too quiet. It always got a laugh.