“I think Everyone has their opinion sounds better than Everyone has his or her opinion. And nobody says whom. Why should I write that way?” Over time, the conventions governing certain usages have become much more relaxed. To many Americans, Whom did you talk to?—which is technically “correct”—sounds unpleasantly fussy. However, other people object to less formal constructions such as Who did you talk to? Unfortunately, you can’t please everyone. Use whatever constructions you are most comfortable with in speaking, but be more careful in your formal writing. If you don’t know whether your audience will prefer more or less formality, try recasting your sentence.