Relatively few people here have a problem with Pinterest making money; the problem they do have, is making money by modifying the links the users are posting without disclosing that modification.

I'd be somewhat squicked if I saw that paragraph in the T&C when I was signing up, but at least I'd know and be able to decide if it was worth it. But by going ahead and not putting that disclosure anywhere; Pinterest has shown that they don't respect their users. And that may be somewhat poisonous to their prospects (or not, Facebook being the prime example).