I am not sure about corruptive power of corporations as a theme this season, but, interestingly, one moment this February I had to tell myself, “Stop. What are the Good and the Evil, again?” Before it was more or less clear (from the characters POV): W&H, vampires, everybody who tries to end the world, or to change it to suit their whims are Evil. Angel fights evil and tries to be/do good. Same with his friends. Now – yes, W&H has definitely helped, but they are going the route defined by their own problems, insecurities, etc.
Yet as characters’ distinction between good and evil is slipping, ours as of viewers, too. Those arguments whether Knox is good or evil – according to previous disposition, he is. Now? He is no worse then Gunn, Wes, or Angel.

Also, there was a lot of mirrors this season – literal and metaphorical. This season mirrors the last one, The Shells mirrors The Hole In The World, the mirror in Fred’s room, Lorne with the mirror, smoke and mirrors, and everything mirrors Angel, who cannot see his reflection, of course.