My guess is that it's the bloatware from AT&T

Seriously, though, I wonder if it's the additional software customization that the operator needs to remove / fine tune the user experience for their networks. For example, on my Lumia 800 I had full wifi tethering without paying for it because it was a developers device. On my 920 it's looks and works exactly the same way, only now it seems to make an authentication call to AT&T after you switch on the server. Several seconds later it turns off and says I've not pay for the service.
Therefore I wonder if the "Extras" are were AT&T add these little tweaks. Any one know if the developer devices have this entry?