Shame @ this google play advertisement on wpcentral !

I don't think the ads are "smart" enough to tell which Mobile Nations site they are on. I believe that they use the same ads (in rotation) on all of the sites. I've seen Windows Phone ads on Android Central in the past and iPhone ads on CrackBerry.
 
I agree it's probably just a general ad. However, even if it was intentional, it would make sense to advertise to your competitor's customers.