In the end, there are a number of reasons. But one big factor is the fact that European tour companies do portray the climb as a "long walk" that anybody who is in good physical condition can accomplish, with no previous climbing experience. The mountain also has extremely easy access -- teleferiques (gondolas) can take climbers up the first 9,000 feet or so. As a result, many of the 20,000-plus people who attempt the summit each year are inexperienced or completely novice climbers. They rely on the expertise of paid climbing guides to get them up and down the mountain safely.

The advisability of having paid guides take climbers up challenging mountain peaks that they are unqualified to attempt themselves has been a hot topic of controversy in the climbing world ever since the 1996 Mount Everest disaster, chronicled in Jon Krakauer's book Into Thin Air, in which 8 people died. In Europe, however, using paid guides to assist climbers is a time-honored tradition. The first ascent of the Matterhorn, in 1865, on the Swiss-Italian border, was a guided climb. Worth noting, perhaps, is that four of the five "clients" perished on the descent. But while guided climbs of peaks like Mount Everest may have become a far more popular (and highly paid) phenomenon in the past 20 years, relying on the skill of a guide to get recreational climbers safely up and down a mountain is the accepted norm in Europe.

That doesn't mean the practice is without risks. For one thing, it makes the slopes of mountains like Mont Blanc crowded in the summer months, since the number of "qualified" climbers is much higher than if only those capable of scaling the peak themselves were attempting it. Aside from the environmental cost of that many humans on a mountain (an issue even at places like Mount Everest as well as Mont Blanc), so many climbers means more people are exposed to more of the risks that a high-altitude mountain presents. There were, for example, 28 climbers caught by the avalanche on Mont Blanc on July 12.

The crowded slopes also mean competition for footing in narrow places, as teams attempt to pass each other, and long waits at some points for access to passageways -- which means that climbers are exposed to high-altitude health risks, as well as cold and bad weather, for longer periods of time.

The crowded nature of Alpine peaks like Mont Blanc means that spots in the overnight huts along the summit route are difficult to get. So if a team has a date reserved, and the weather looks iffy or someone doesn't feel good, there's still tremendous pressure to "go," because rescheduling or delaying a trip is difficult. Added to that is the pressure paid guides are under -- especially in Europe -- to get their clients up and down as quickly as possible, so they can get to the next group. One American climbing guide I spoke to referred to this approach as the "production line" approach to mountain climbing. But that pressure to get the climb over with as quickly as possible, and push as many people to the summit as possible, also adds pressure to the "go" decision, regardless of conditions or how slow some members of the group are moving.