I didn't read every post on this topic, someone may have brought this up already but let me give you some examples of situations where noise have caused an issue outside of sleds.
First I live in the Texas where we normally get to do what ever we want......
1. My sons car (nissan 350z) and 3 of his friends cars (Mazda Miata, Subaru WRX, and Ford Fiesta) was impounded by our local police because they received several noise related complains about the cars driving through neighborhoods. On their way home from school they were stopped, ticketed, and cars impounded for violating the city noise ordinance. The cop had a noise meter, judge upheld the ticket, total cost was $1800 (ticket$300, towing $350, new exhaust $1000, and mechanic certification $150).
2. Buddies jet boat ticketed $500 and banded from our lake for exceeding noise limit after the ranger received noise complaint calls from residents on the lake until he gets it tested by the ranger.
3. My neighbors home stereo exceeded city ordinance and he was ticketed $300 after neighbor complained.
If you think for a second that loud exhaust will not cause issues, your live under a rock. It doesn't matter how much better the performance is, it isn't worth losing your ability to ride. I know we all want to be like "Tim the Tool Man Taylor" with more power but at what cost?