The survey addressed players as young as 8, and found that the largest group of players in the U.S. is comprised of 8-12 year olds. That may come as a surprise to many players whose idea of a console or PC game isn't really geared toward children, but makes sense when you consider games and virtual worlds such as Virtual Family Kingdom, Free Realms, and any console game with Mario in the title.
Delving further into the MMO side turned up some interesting information. Of the US players surveyed, 21% said that they play MMOs, and 45% of those players define themselves as paying customers -- presumably that includes both subscription models and gamers that take advantage of cash shops. In spite of the large percentage of paying players, a free-to-play model is one of the biggest factors for those considering a new game. The rising success of many games in the past year that use a free-to-play model seems to support this.
Worlds In Motion offers further number crunching, and if you're interested in seeing the full survey report, gamesindustry.com offers it for a fee.