The ESRB has decided that they can no longer keep up with the volume of games that are released, so will move towards an automated system for rating releases.
Previously, every game was vetted by a independent panel, and a report would then be written detailing exactly why a game received a rating. Now, publishers will be given much more power, as they will have to fill out a digital questionnaire which will then be used to determine the rating the game receives.
It might sound quite different, but previously, the independent panel never actually played the game. Instead, the publisher would send them a DVD which contained content which they deemed to be worthy of consideration.
Source: NY Times