I actually know someone who put two rubber bands on his trainer's wing (he didn't have a rack or carrying cradle) just so it didn't lay on the ground or blow off his car. One thing led to another, and he actually wound up doing a take off run when he realized his mistake. Close call...
Also I guess it's been stressed here quite a bit, but I'll mention it again, as I'm taxing out to the duty I always walk behind the plane and check the control movements one more time. I lost one due to reversed alierons, will do my best to ensure it dosen't happen again!