"Do your homework!" says Scott Mendelson at Film Threat in response to Roger Ebert's rules for critics. This is less scathing than Ebert's article, but he details how some critics make assumptions regarding how much or how little a film made:
I jumped over Dennis Harvey of Variety back in September for lazily assuming that Changing Lanes was a box office disappointment while Crash was a mega-smash (they both made about $95 million worldwide). It’s a common phenomenon, especially when dealing with alleged financial success or disaster. But don’t just make blanket statements that aren’t backed up by the facts. And don’t call a movie a critical failure when its failure was merely financial. And don’t brand a movie as a financial disaster without actually checking the numbers. This happens most often when writers want to appear snarky and cool by trashing a film or actor. It’s amazing how rarely writers make mistakes that prop up a film or filmmaker.