What font is used in the Stack Overflow logo?
It's called FF DIN.
Just to confirm -- it is FF Din, as Ólafur noted.
I suggest trying What the Font?
In addition to the official FF Din, as Ólafur said, these are the closest matches I found installed on my computer:
I don't know what these fonts came with, but here are some possible candidates on my system that comes with a bunch of fonts:
- Windows 7 Professional SP1
- MS Office Professional Plus 2010
- Adobe Reader 9.5.1