The NAIA is following the NCAA's lead in requiring that only bats conforming to the "Coefficient of Restitution” standard will be legal for use, starting with the 2011 season.
Coefficient of Restitution bats are less lively than existing aluminum bats, and are intended to produce the same batted-ball speed as a wooden bat.
Now, what does this mean?
First, any aluminum bats you now have in your closet are illegal. You may as well ship them off to a baseball-playing Third World country such as Cuba, Nicaragua, or Guatemala.
Bats which conform to >the "Coefficient of Restitution” standard will have a stamp (shown here) that can be checked by the plate umpire when a player steps up to bat.
A team currently batting .280 will be batting about .220 instead. There will be fewer blowouts, which is good for the game. However, teams with strong pitching will have less of an advantage.
The NAIA considered alternatives. One of them was the wood composite bat, which is close to unbreakable and cheaper to manufacture that an aluminum bat. However, with the NCAA using Coefficient of Restitution bats, there wouldn't be any economy of scale with wood composite bats, and there would also be a potential liability issue.
The biggest losers in this change are the bat manufacturers. They have spent some serious bucks on R&D over the years to develop better (i.e. livelier) products. Now, all bats used in college baseball will be the same, whether they come from Easton, De Marini, or Louisville.
Follow-up article: Coefficient of Restitution bats after one season