People don't use enough commas. I've been using and abusing them since at least high school English class, but I've managed to winnow out most of the superfluous ones over time. The one I find missing most often is the one that belongs in what I guess is called a vocative statement where someone is being addressed. People are omitting it from its proper place before the name of the addressee. It doesn't look right and it's confusing in certain contexts.
Don't you agree, gentle reader?