When showing a property there is a lot of responsibility on the Realtor to make sure their clients are aware that this is someone's home and although you are there to look at it, the owner's personal property should not be tampered with. This can be a problem when the buyer clients are distracted and are not keeping an eye on their children.
I recently had some sellers who were sitting in their car across the street and witnessed unsupervised children gleefully jumping on the trampoline, riding their children's bicycles, and found that the children had been playing with items inside the house and misplaced them. It would have been a problem if someone had gotten hurt, or if the seller subsequently found something missing.
It is best handled by the Realtor setting the tone for the showing before opening the door by saying 'we must all stay together as we walk through the house. The seller is letting us look, but we must not touch their things.' There is a reason Realtors are checked by the FBI and State Police before obtaining a license; we are going into people's homes when they are not there, with all of their belongings.
On the Listing side, to limit exposure, Realtors should inform their clients to secure belongings that might be attractive to theives: jewelry, firearms, prescription medications, tools, expensive toys and small electronics should all be secured when you are anticipating a showing.