Hi Dave
No official evangelists as such, but plenty of people all over the US and Europe are willing to talk to the platform.
We do have a Community Team of which myself and Carolyn are members.
Check out an interview I did with Shari Thurow and ClickZ to explain what our team does in a little more detail:
adCenter Community Team Interview
Cheers and keep posting! 
MelC - adCenterEU