Trivia question: Will a battery be damaged if stored on a cement floor?

See if you can answer this correctly.  So many times someone will tell me as I set a battery down on the floor in the shop;  "Better not set that battery down on the cement."  So, I dutifully find a piece of wood and set it on the wood.  Now here is the question:  Is it important that I set the battery on a piece of wood or not?  Do you know the answer?  Why do so many people think that setting a car battery on cement is bad for the battery?