I was going to respond a few hours ago to your post: "maybe you should." There's a fine line here between being cruel and being honest. Personally, I've always struggled with this idea with some of my wealthier friends that act "more polite." They often out-right lie to each other, constantly, over little things. It's so weird to me. But when it comes to business, you shouldn't lie when providing advice or feedback. At the same time, you don't want to put people through an interrogation or completely crush them ("no, I don't like your idea, etc, etc, etc"). I think Paul Graham walked the line very well.