It does work, but if it becomes loose, you can lose your data. I spoke with Jay about the penny. Copper conducts well, yes, but foam WONT conduct and lessens your chances of getting a shock. Thats why they say use cr2032, not cr2025 because kids have been known to put in random things that fit... In this case, the penny. Also, it can corroad your battery faster or conduct with the coin/penny in a not good way.
So if you are putting something in with it, use foam. (art foam is best)