There are many things that are unpredictable when climbing a mountain. Sometimes you are just in the wrong place at the wrong time - we have no control over mother earth or nature. From the reading I have done, the deaths on K2 might have been prevented if the ropes had been fixed properly. The time taken to refix the ropes on the mountain delayed everyones' summit. However, the risk of an avalanche or a serac falling at any time exists on any high altitude mountain. Most climbers realize that if you climb long enough the mountain will eventually take you. I am sure these catastophes really make people wonder why people climb at all. I cannot answer that question.
I extend my thoughts and prayers to the families of the K2 climbers.