That said, I haven't actually bought one since Final Fantasy XII over a year ago. I did Galaxy completely on my own, only checking the internet for a single star that I couldn't find.
But speaking of which, the only strategy guide that was completely useless was the one for Final Fantasy IX seven years ago. Pretty much half the book told you to go online to find the answers to all of your questions. It was supposed to be this amazing new high tech way of integrating paper strategy guides with online connectivity, but all it did was piss off everybody who'd bought the book only to find that it basically told you nothing except to go to the computer.
EDIT: I have to admit, though, that I had a similar experience in GameStop yesterday when I encountered a hardcover strategy guide for Super Mario Galaxy. I'd previously seen one (imitation leather-bound) for Phantom Hourglass. Now say what you will about strategy guides in general, but that is certainly a waste of money. Or for people who mistake gaming guides for actual literature.