This video isn't new, but it's new to the public. Microsoft made this video last year but it was used internally for its internal Global Exchange sales conference last July. In light of the recent change to Google's privacy policy, Microsoft has not only taken ads out in local newspapers criticizing Google, they have made the "Gmail Man" video public.
The video shows a mail man looking through letters to find keywords for ads. The spoof is obviously targeted at Gmail's practice of showing keyword ads that related to your email. In Microsoft's view, Gmail is reading your email.
Microsoft has posted the video on the company's Twitter, Facebook, and YouTube pages. On their Facebook page, Microsoft asks, "Would you trust this guy to deliver your mail?"