In an interview last week the actor Seth Rogen, reflecting on his brushes with bad reviews, said: “I think if most critics knew how much it hurts the people that made the things that they are writing about, they would second guess the way they write these things.” The Guardian’s film critic Peter Bradshaw came to the defence of “bad notices”: “Of what value are the good reviews… without the bedrock assumption that the reviewers were free to say the opposite?” The exchange dredges up an old question: who is criticism for?