A March 1 article in Telegraph.co.uk, Revealed: The secrets of belly button fluff, reports that "the scaly structure of the hair enhances the 'abrasion of minuscule fibres from the shirt' and directs the lint towards the belly button."Doctor Georg Steinhauser goes on to say that hair scales "act like a kind of barbed hooks" (Velcro?)
Shaving one's belly hair will result in a fluff-free navel, and a belly button ring seems to also be effective at sweeping away fibers before they have a chance to lodge.
An earlier Australian study determined that the "typical" carrier of navel fluff is "a slightly overweight middle-aged male with a hairy abdomen."
I'm going to see if I can have my belly button declared as a national breeding ground and sanctuary.