No photographer would ever allow his/her camera to be passed around under different handlers (note : I do not use trhe word 'photographer').
There was a case of a colleague who had just bought a Nikon. In the office , everyone was naturally excited. His camera was passed from one handler to another . After about five handlers, it was returned to him --- with finger-prints on the lens. He almost cried.
On another occassion , he gave a lift to his colleagues. His camera bag was on the back-seat and his colleague nonchantly 'passed' his camera bag to the back of the seat ! Poor guy ! He was lost for words to see his expensive toy being handled that way !
The dslr is made up of hundreds of sensitive components, electronics and otherwise. Synchronisation can run foul if they are given just a hint of rough handling. This is further exagerated when the poor camera went through a few hands , who, quite innocently without any malice, but more ignorently 'tried' the camera !
A quote from one of the websites...
'I love my camera, honestly I never leave home without it, you never know when that perfect shot will turn up and it's really annoying when you see something amazing and think "I wish I had my camera". But if like me you do carry it everywhere then you need to take good care not to damage it or let it get dirty. In this section I will explain how to clean your camera and protect it from getting damaged.'Yes----you can take all the steps to care of your dslr -- but it would come to noughts if you are not if you neglect for a second !
To me , its not about selfishness. I only allow two or three person to take photos from mine .
Anyway....just my Sunday morning thoughts .....