Y-O-U-R...Y-OU-apostrophe R-E: they're as different as night and day...don't you think that night and day are different? What's wrong with you?
-Strongbad (click on the beefy arm in the last frame of the cartoon for this and other 'rhythm and grammar' tunes.)
The Guy got into another proofreading pissing contest the other day. Corrected some bad punctuation on a Christmas card he was typesetting, then had the job bounce back because the customer didn't like his removal of an apostrophe. My grammar ninja refused to budge on this, citing one of his unimpeachable sources (rule #9, to be precise).
I'll admit fully to having problems with punctuation: colons and semicolons in particular give me headaches. The use of the apostrophe/posessive vs plural puzzle seems a bit of a no-brainer, however.