Obviously SO is just part of a larger community, a Justice League if you will. But it seems there's a secret member of the league, The Daily WTF. They're even giving out SO stickers at Daily WTF events? Alex Papadimoulis hangs out here. So, is there going to be an official relationship between the two? When is the coming out party?
I'm not sure of the exact relationship, but I know Alex Papadimoulis is the "ad guy" for Stack Overflow. I have no special knowledge of the situation, but I suspect it's just a "standard" relationship with Inedo Media, assuming Inedo has been around long enough (since 2008) to establish such a thing.
It's also interesting that the Inedo site mentions that they aren't seeking new sites, so it could be that they are very happy to essentially be the exclusive ad firm of DailyWTF and Stack Overflow. And it's odd that Super User isn't included there, as I suspect it's much more popular than Server Fault.