Untreated decks dangerous?

Deck Maintenance Deck Repair: "decks are subject to the damaging effects of weather. A poorly maintained deck quickly turns a drab gray color. The discoloration is caused by dirt, moss, algae, and other plants, which soon begin to tear apart the surface of the wood. Splinters form, creating a rougher surface that is even more inviting to dirt and plants. Before long, you have a dingy deck that's treacherous when wet and riddled with splinters. "