Ok now my Serious answer as this post.
This one is a bit topical for me at the moment. After I very recently Tossed Jeff's FZ1 up the road & put myself in hospital for a coupla weeks with a punctured lung & fractures to my shoulder & ribbage.
I didn't offer "Tiggr" to Anyone until he had a few minor marks from stuff that happens. Then i was/am very selective in whom i would let ride it. I think only 4 people have ridden "Tiggr" in the 2 years Since i bought him.
My '91 FZR6 on the other hand is on loan to a Friends Missus for her to get some confidence before she gets back on her 05 6r. Janelle Dropped it about half a dozen times when learning purely cause she was too short at intersections etc. Yappa rode it last Track day till Lunch time & I rode it in the afternoon sessions(shows how much i trusted Yappa). I also rode Barrabob's & Varden's 6r's the same day. I had also Swapped Hemi for the 7r the track day before & our times were only a second slower then on our own bikes after 2 sessions.
I dont think dropping a friends bike has to be a negative experience, as long as you are prepared to accept responsibility for it & do the right thing. Jeff & Anne were always more concerned about my injuries then the bike & I feel if anything we are better friends now then we were before.
I have ridden a lot of borrowed bikes, mostly at the request of the owner for one reason or another. I had too ride my mates Fireblade home from the bikeshop as he didnt have a licence, Had to ride Kevs Monster 12r back from a Dyno session in the wet through Peak hour traffic etc etc. A few i've asked to ride & I must admit it felt good when they said it was OK to have a ride. It's nearly as good a feeling as when you return them in one Piece
As for the future I'm not sure if my recent experience will change how i feel about riding other folks bikes till i get out there & find myself in that position.
As always it's a motorbike & they do Fall over, can happen to anyone at anytime. As withthe rest of you's I'm just trying to keep the off's as far apart as possible.