Under certain stressful conditions, these layers can become separated. Most often, the topsheet will start to peel back from the underlying layers. This is called delamination, and chances are it will happen along the nose or tail of your board. Mild to moderate delamination can usually be fixed by a qualified repair shop. If you notice stress cracks radiating from the nose or tail of the topsheet or congregating around the bolt holes, it's time to make an emergency trip to the repair shop.
Stress cracks can spell doom for a snowboard if they involve layers other than the topsheet.
And since the untrained eye often cannot tell from where they originate, it's better to get those evil little things looked at. Edge maintenance is also important. Most edge blemishes are cosmetic, but it's wise to get them filed out before a few small burrs turn into an edge that looks like the Abominable Snowman chewed on it. It's also a good idea to get those edges sharpened on a frequent basis. Sharp edges turn better and ensure a solid purchase as you fly over ice patches.