The problem is any of the stuff like shelving or say a load bearing surface like a desk. Those flat surfaces are almost always MDF or whatever cheap engineered wood products IKEA uses. The furniture looks nice initially, especially for the price, but the horizontal surfaces always sag after 2-3 years even under low weight. I have a dresser, a desk, and shelving that all developed this problem and some of the shelves barely have anything on them.