UPDATE: It’s been shaky, but back up after nearly two hours of all systems down. AdAge estimates that Amazon lost about $2 million in sales:

E-comerce site Amazon went down this afternoon around 1:30 EDT and stayed down for at least an hour. Attempts to access Amazon.com were met with the following message: “Http/1.1 Service Unavailable.” It’s hard to know exactly how many dollars a minute Amazon loses in sales for every moment its site is down, but simple math pegs it at about $1.8 million an hour, based on Ad Age estimates.

Amazon’s Canadian, UK, and German sites are all fine — appears to be only U.S.-based.

Twitter is also down. Cloudy day on the internet? Or is it something else? more at CNET.