Most fun exchange I've had so far...while riding the tandem home alone from the bike shop, got a comment "where's your passenger?" I turned around, looked behind me with shocked look on my face and exclaimed "Oh my Gawd, she musta fallen off !!!"
Got a stunned look, then a good laugh.
We pull a trail-a-bike (with a kid on it) on occasion, and we certainly get alot of waves and smiles, and like some said, the cars give us a bit more room.
Give me two!