funny...I was just about to post something to that effect! Many MC riders remove their turnsignals completely for 'style' and rely solely on casual handsignals to communicate. The only problem is almost no one knows what the hand signals mean any more! They don't teach them in driver's ed or test them on the license exam and they haven't in years, AFAIK. Me, I want the guy behind me to know what I'm doing...
There are a lot of guys who ride around with their arm or hand out the window so you really don't know if they are signalling or not. If I am totally honest I spect some gals do it too.