Reason #4356: Cool young hipster at Labor Day protest parade points at Prius, points at me, and says "That's hip." (I'm hip! Who knew?!?)
Reason #4357: after getting a manicure, I can leave the keys in my pocket, and still unlock the car and drive away without marring the nail polish!
Sign that Prii are officially ubiquitous? Finding a parking place at Target, and ending up nose to nose with another one.