Did you guys see this? Some folks at 4chan were, well, 4channing:
They sent this e-mail to firstname.lastname@example.org
The next day, presumably Gabe wrote back with this:
I can't atest for the truthness of it all, and maybe a really angry intern is taking care of Gabe's e-mail account. If it's really Gabe Newell though, I just hope he doesn't think our favorite thing is a new Day of Defeat or something.