There are some very disturbing stories about extreme conditions in the warehouse.
There's a good NYT article about it (http://bits.blogs.nytimes.com/2011/09/19/inside-amazons-very...)
This is the piece I heard about:
So many ambulances responded to medical assistance calls at the warehouse during a heat wave in May, the paper said, that the retailer paid Cetronia Ambulance Corps to have paramedics and ambulances stationed outside the warehouse during several days of excess heat over the summer. About 15 people were taken to hospitals, while 20 or 30 more were treated right there, the ambulance chief told The Call.