Here is my recount I heard from Valve of the events that took place:
1800 EST - Lead programmer at Valve issues the force update
1830 EST - Force update complete, lead programmer sits back and idles in his glory
*MEANWHILE - 1840 EST*
//ACTUAL CONVERSATION WITH VALVE EMPLOYEE//
[21:19:38] killermonkey01: oh man I bet Gabe was eating a jelly donut playing GE:S
[21:19:42] killermonkey01: then he went to change servers
[21:19:44] killermonkey01: and was like
[21:19:46] killermonkey01: WTF!
[21:19:51] killermonkey01: and called his top programmer
[21:19:57] killermonkey01: and choked him through the phone
[21:20:03] killermonkey01: then he finished his donut
1900 EST - Servers across the world start failing, CSS, DOD, TF2, everyone who has jacked out of the steam network cannot jack back in
1930 EST - Sentinals are released to clean up the rest of the horde
2000 EST - The Earth Stands Still, in an eerie silence, as Gabe steps up to the microphone at the State of Valve address and announces that all video gaming has ceased to function because Steam is blocking all of the connections.
2030 EST - Steam starts to evolve, now everyone's computer is a slave to the Steam empire, GE:S suddenly starts working again, the only game available in the world.
2100 EST - The world calms down as they enter a new era in gaming...
I mean this is completely plausible, but then again, it could have been some jack ass tripped over the power cord to the logon and authentication server at Valve Headquarters...