From the Nextel Commercial, a dot is an underling, a subordinate, a person performing a specific, limited function (e.g. a pizza delivery person).
Dots get agitated, and you don't want to agitate them. You don't want them making decisions either. The best case is where
you've given them just enough management to perform their tasks smoothly and have appeared to be very responsive to their concerns and needs. This keeps the dots happy.
Everyone is happier when the dots are happy.
"You shouldn't have given him the whole presentation, he's a dot. Just give him the page he needs to work on."
"Why would you expect them to remove your desk before they put in the new one? They're dots, you told them put, they put."