That was an internal video to try raise morale in Microsoft and get some people switch, it's pretty safe to assume gmail reads your emails as much as their spam filters does. But as well as doing the spam filtering on the results it does ads.
Ads can be disabled for Google Apps accounts, but as should be obvious any provider that provides spam filtering will already be "peeking" at your email. Perhaps in part to their ad relevancy system, Google's spam detection is best of breed.