why would you run the bike without an exhaust. it sounds like crap, no tone, just loud. your only going to attract unwanted attention and people are goin to look at you like your retarted. bikes with bigger displacment can sometimes get away with no exhaust because it is very deep and actually sounds decent
you are porb seeing it on the R6 06 and up.... they have the cat in or just after the headers. so times they just have a straight pipe stub like this or use no pipe at all and it looks like no exhaust. if you do it on other type bikes you will lose performance and gain only loud noise.
The muffler is actually under the bike to get weight lower in the bike. I have a straight through exhaust w/o a muffler. It doesnt bug me. I like to whack the throttle when i ride by people on their phone with the windows down. With a Power Commander on, it doesnt backfire and actually makes pretty decent power.