AT&T Buying AppNexus?

According to Cheddar, AT&T is rumored to be buying AppNexus.

Given the recent merger between AT&T and Time Warner they have a tremendous amount of supply that they need to monetize. The thought is that with the increasing digitization of TV through OTT and Internet delivery, with a digital ad partner, they can re-invent the TV ad sales marketplace. With Google and Facebook dominating the digital ad sales market, they need their own turf. Why build when you can buy?

Take a look at some of the most relevant coverage: