Mike Trapp at College Humor has a whole set of new marks we should just be able to slap over someone else's typing whenever someone is wrong on the internet. The misuse of the word "literally" gets under my skin, but the funniest part of the article is where you get to correct someone else's correction. Link
theory and hypothesis
proof and evidence
His "I think that the Sopranos, is the show..." - Commas as breath marks (which was once actually taught!).
One of my pet peeves: using famous and notorious as synonyms.