I'm constantly taken aback by the punctuation I run across in ordinary copy. The overuse of em dashes, alluded to earlier, is a common problem, but the worst error to me is poor usage of commas. Too few writers seem to consistently put them in the right places, particularly, it seems, to separate independent clauses; the result is a run-on sentence of sorts. I find that in proofing copy, taking commas out or inserting them is probably the biggest activity. Does it really matter? Yeah!