Vendors who drop a proposed project schedule in front of you and then get hurt/defensive when you explain that their project isn't the only thing you've got to accomplish over the next six weeks.
Vendors who drop a GoToMeeting in front of a member of your staff and then get pissy when he can't drop everything and participate because (wait for it) that meeting isn't the only thing he's got to accomplish over the next two hours.
Bookmarks