yeah im with you dave, when people aske me what type of car i have i tell them i have a nissan and leave it at that.
people have expected lifts from me in the past. just make it clear that because you can drive doesnt mean your a taxi. They are responsible for themselves... its not your worry. i only pick people up in emergencies, ive only done that once and that was when my mates girlfriend broke up with him and kicked him out in the rain at 1am.