In HOH, Harrington says that you should always call on the button when playing HU. This is because you have position and because of the 3 to 1 pot odds.

I watched some CardRunners videos and in that you see them folding a lot pf on the button. Also, if you watch the high stakes games on FullTilt you also see players folding on the button. In the CardRunners videos they even mention that never folding on the button is a big flaw in many players games - and you know that you are playing a weaker when the call/raise every single time on the button, but never fold.

When do these 2 pieces of advice apply. Are they referring to different situations? (ie. cash games/tourneys. deep/short)