As fresh-from-the-hen eggs become more available at farmers' markets and as more people jump on the backyard chicken coop bandwagon, peeling hard-boiled egg shells may become trickier. According to Wired Science, fresher eggs are scientifically harder to peel. You may think you're a pro-peeler, only to end up with a crater-filled blob. As Harold McGee points out in On Food and Cooking:
The best guarantee of easy peeling is to use old eggs! Difficult peeling is characteristic of fresh eggs with a relatively low albumen pH, which somehow causes the albumen to adhere to the inner shell membrane more strongly than it coheres to itself.
But don't worry—this doesn't mean you have to cook questionably spoiled eggs. Just put the hot eggs into a bowl of ice water for a few minutes first before peeling to help loosen up the shell a bit.