Sort of the uncanny valley for intelligence. It astounds me how many people don't trust programs/automations when it is almost provably better at performing a given task. http://en.wikipedia.org/wiki/Uncanny_valley
In this case I think it's more a case of incentive structures, and not trusting the agent's motivations.
In this particular case the problem is that the virtual valet would, unlike a real valet, be funded primarily by kickbacks from whatever services he winds up booking for me, so I've got no reason to believe he's making decisions in my best interests instead of his own.
Basically if I'm going to trust someone else to make my decisions for me, I want a real flesh-and-blood person that I can shout at if things go wrong.
In this particular case the problem is that the virtual valet would, unlike a real valet, be funded primarily by kickbacks from whatever services he winds up booking for me, so I've got no reason to believe he's making decisions in my best interests instead of his own.
Basically if I'm going to trust someone else to make my decisions for me, I want a real flesh-and-blood person that I can shout at if things go wrong.