well i was an avid motorcyclist for about 4-6 years... then i noticed i was always riding my bicycles and sold my motorcycles...
but... first, i have to say that although the sound of the Harley is distinctive and all i have never found it very appealing... now the Ducati i must admit...
and then there's the sound of a well-tuned Ducati 996, or 999 with a carbon fiber ferracci exhaust... which sounds like a chevy 350 w/ a lumpy cam & glasspacks. Then you wonder "why am I riding this harley?" as the guy on the Ducati blows past you... leaving his heaven-sent big-twin sound right into your eardrums.
and i have to admit that when i was in college my motocycle exhaust system rusted a hole and got loud... i decided it was "cool" and i bored bigger holes. on my next bike i wanted to buy the "loud performance exhaust" (K&N i think) that was also a performance improvement, but cost like $500, so i just bored some holes in the exhaust (note: this doesn't affect pollution as motorcycles have no catalytic converter and it just dampens noise) ---- i used to ride with the "goal" of setting of at least a few car alarms per ride (just weak the throttle as you pass parked cars)
these days i occaisonally find loud motorcycles annoying, but i find it hard to be really critical as i did the same thing 10 years ago...
although the posers who can't ride are annoying: "look how cool i am on my loud bike (that i can hardly steer our of the driveway)"
there are laws that regulate noise levels, but most are not enforced. i never once even got a warning about my loud pipes, although my loud pipes increased my chances of being ticketed by police b/c it attracted attention and draw attention to me and my bike