2blackbelts, oldiron, you guys are missing the point.
Is there really gremlins that will make a biker have a bad day, of course not (that we know of anyway). The bells are just a "something" that are in vogue. Much like the those 80 year old drivers who wore extreme gauntlet gloves with tassels hanging down looking like a 1930's Hollywood cowboy or in the 40's and 50's those nifty little "biker" caps that are the fashion rage with the some alternate lifestyle fashionistas today - big back in the day, now not so much.
Like this thread, the bell craze will pass until the next fashion statement comes along.