[Bring_Back_Shantz]

The only advantage I can see of this is the fact that a small minority of people will tell the manager that the service was bad.

The problem with people not tipping to show their satisfaction is that it rarely if ever gets the message across.
Seriously, what do you think your server says when you leave a bad tip:

a) "Gee, I guess that gentleman was upset with the quality of my service, I shall endeavor to do better in the future."

or

b) "What an a#####e!"

So if the automatic tipping actually got the message across it'd be a good thing. However I highly doubt it'll be any more effective than the old method, as most people will probably just say "Screw it I'm never coming here again".