There have, even in recent years, been disastrous years where entire parties have been lost. Here's a list of the deaths: http://en.wikipedia.org/wiki/List_of_deaths_on_eight-thousan...
Many more than that number come back down being carried by their friends, with lungs full of fluid, brain damage, black fingers/toes/hands/feet/noses which need to be amputated, or other serious injuries.
A fantastic read is "Into Thin Air" by Jon Krakauer, which covers a really bad year for climbing on Everest.
The second summit team, Alison Chadwick-Onyszkiewicz and Vera Watson, died during this climb. (Vera Watson was survived by her husband, the computer scientist John McCarthy.)[5]
Here is a good read that talks a bit about it: http://dsc.discovery.com/convergence/everestbeyond/diaries/g...
[edit]My bad, that was not Mt. Everest, that was an expedition on K2.[/edit]