Modman - I am with Brad on this one and in the camp of kind of don't get it. There are landowners who don't want loud pipes going through their land. My perception of folks with loud pipes, is that they do crank the RPS's at the wrong time, way too many times. I understand you like the sound - I use to race MX and believe me, all my machines were modifed then. However, with the push to keep as many trails open as possible, I simply see any machine modified to be noiser than stock is the problem, not the solution.
You mention harley's as well. Now I fully admit I am putting all into one basket, but the last house I lived on was a popular ride for bikes. All bikes would come around the corner I lived on and drop a gear and bring the r's up. Harleys would be so loud (the ones modified at least) it would wake up my childern at the time. In summer, if they were sleeping, we would need to keep all the windows closed and would still have issues. So when folks comment with pipes that they are respectful and go quiet near homes, I simply don't buy it.
I know I am over simplifing, but be part of the solution, not the problem.