because steam isn't one server, it's a cloud of many, if one part goes down, others in different regions pick up the slack, while there maybe a local loop issue with a given place, as a whole it doesn't crash on mass, that would take a massive hack or DOS, which to date hasn't happened ever in the history of steam.
as you login from a given region, if you region goes down for any reason, just change regions for downloads or signing it, then it works.
regarding the story above, look at the comments on steam, it has 25 on one and 30 on another replies, so is that a mass fail?
with 10,613,733 members login in the last 24/48 hours, if it was a major issue, more than 30 would be complaining.
regarding downloads amounts, here's the information
world wide it's 5.6 Tbps, you will need a few 0 to work out how much data that is
< Message edited by zakblood -- 12/26/2015 4:32:19 AM >