Originally Posted by Kimmo

My experience is a bit different - I've found the tabbed washer in many cheaper headsets prone to trash the threads, to the point it's often more trouble than it's worth; I've resorted to filing off the tab more than once. And I haven't had any problem with these headsets working loose once properly tightened, minus the tab.

Nicer gear has a raised lip on the cup around the edge, preventing the washer from stretching and allowing the tab to ride up over the threads; on these the design works as intended. It can even be possible to lock such headsets in place with a single wrench, in a pinch.