Some people do on their p5's. On our cars it is a natural result of the way that the hose that carries the windshield wiper fluid was built into the car. It should only happen when there is still wiper fluid in the hose, in other words, when you have recently sprayed the back window. If you don't use wiper fluid on the back window, the hose will pretty much dry up and you shouldn't have any more fluid streaking. I haven't used the rear wiper fluid in months and subsequently haven't had any streaking in that entire period of time.