Yeah.. what could possibly go wrong right? A nice conversation to get to know them for a whole 30mins, that will surely be enough time for you to feel them out.
I am sure you will find plenty of opportunity to ride at the back of someones bike, hopefully it doesn't end badly for you. I would never suggest this type of behavior for any of my friends guys or girls. It's just not safe. If something were to happen and you go down, the riders insurance will be pretty messed up as well. Its just a HUGE risk for really not that much. Good luck.