I'm not sure if it's globally widespread, but Google Adwords has been making direct sales pitches to manage large brand's accounts, in competition to agencies. The pitch is generally, deal with us and you'll have more money to spend and we can do it better. Well they don't have to account for the same profit margins that an agency has, so it's likely they could be more competitive.
Often this goes with Google approaching and sometimes recruiting a person managing a major account, previously in an agency environment with added incentives.
Have any account holders, or agencies effected got a view on the relative efficiencies and risks.