When writing, you want to show that you have the greatest command of your language possible and that includes knowing how various parts of a sentence affect each other. The problem with “who” and “whom” is that a little knowledge can be dangerous. You might think it erudite to use “whom” because it sounds more formal, but you can’t just throw it into your sentences willy-nilly. You need to know how “who” or “whom” is being used in its clause. This explanation will make everything clear to you and, even if hoi polloi are using the pronouns incorrectly, you can feel proud of your understanding. Just be sure to apply the same rules when using “whoever” and “whomever.”
