My response:
If this was "Joe Average" then it could be considered trespass if he was never on your property before, and had no business being there. However, someone trying to deliver something to you, or go to your front door, has implied permission. If it was a neighbor, then it could be argued there was express permission.
Insofar as liability is concerned, you have two considerations: Was the excavation "open and obvious"? And/or was the excavation clearly marked and cordoned off?
IAAL
[This message has been edited by I AM ALWAYS LIABLE (edited May 30, 2000).]