I've never owned a motorcycle, but I ride a bike (as in a Giant OCR2) just about every day. Two years ago I was riding my last road bike and was hit by a car, breaking my right leg pretty badly. Since then I've ridden under the assumption that once you get on the bike, just assume that you're invisible.
From what I've been told by motorcycle riders, being slightly larger/louder doesn't make you any more obvious to most drivers.
If you see a late model four door, and nothing but knuckles and blue hair behind the wheel, be very afraid.