I've given a few people rides on the back of my bike before. I have not, however, ridden on the back of anyone else's bike.
This weekend I did. Lady Luck and I dropped our cage off to get new tires put on, and naturally used the scooter as the support vehicle. Lady Luck wanted to practice riding with a passenger (we're expecting guests, and she wants to be able to take them out on the back of the Vespa), and I make a pretty good practice passenger.
I don't have any hangups about riding behind a girl. After all, for all anyone else could tell, the cute scooter chick was just giving the burly biker dude a lift back to his dripping-with-manliness bike.
Lady Luck is a good rider, and if I didn't trust her there's no way that I would have gotten on the back of the Vespa. All the same, shortly after hopping on the back, I got the fear.
Little wobbles that I wouldn't notice otherwise were magnified and I was certain the bike would go over any second. I nearly pulled the passenger grips off the bike, and it took every ounce of will for me to keep my feet on the pegs at stoplights.
Lady Luck didn't have any trouble handling the bike with me as a passenger, I'm just a huge chickenshit. I guess I have some control issues to go along with my thrill issues...
Incidentally, the passenger accommodations on the Vespa are perfect for a guy my size. In a word: spacious. And I have to give them props for installing such rugged passenger grips.
Anyway, I don't think I'll be getting on the back of any more bikes, but I'm not worried about Lady Luck's ability to ride with a passenger.