The results: overuse, not curveballs are to blame for arm injuries.
As mentioned before on this site, it's primarily the young pitchers that repeatedly push themselves to the limit without enough rest in between outings that risk hurting themselves. Surprisingly, some previous studies have indicated that curveballs don't put any more stress on the arm than fastballs.
Still, the calls for banning curveballs in Little League have persisted. But Little League President and CEO Stephen Keener has now concluded that a ban won't be necessary.