It is an evil practice born of corporate interests, just because it could be evilier does not mean we should turn a blind eye to it.
Evil? Really? I can see sneaky, sleazy, underhanded, or even manipulative, but evil? Evil is murdering people because you don't like the color of their skin. Evil is shooting young girls in the face just because they want an education. Evil cutting people's heads off. Evil is putting corporate profits before the health and safety of customers or workers. No one is going to die or become ill because they don't notice the check box. I agree that opt-out instead of opt-in benefits Yahoo at the expense of the user, but if we keep using 'evil' to describe any behavior we find disgusting, the word loses its power and becomes meaningless when real evil comes along.