I am very, very interested in this topic.

I have read and reread Harrington's books. I don't play tournaments but if I understand things correctly early stages of tournaments are similar to ring games.

I don't understand his hand selection though.

He advocates folding small pairs (22 - 55 ) in EP and folding 22 - 66 in MP to a EP raise. For example, if you are in fifth position and the player in third position opened for three times the big blind he says "the small pairs , sixes through deuces, are not playable. Just throw them away. " (page 190, Book No. 1)

Why? What is the difference between 55 and 77? What makes one +EV and the other -EV against an early raiser. You can't do much with them without flopping a set, can you? Is this something that applies to tournaments only?