Bass trapping - corners or walls?

I've been reading articles on the ASC website and it seems that they contradict themselves regarding placement of bass traps. Most of their placement articles discusses placing bass traps in the corners. But the article below actually says that traps in corners are not that important and that traps along the mid point of opposite walls are more beneficial. What gives?

http://www.tubetrap.com/bass_traps_articles/iar89.htm