Blizzards lowest concern is pvp balance at lower levels. Personally I believe people do such just because they can't be competitive where the game and gear is more balanced. If I wanna pvp and prove that I'm good at that class I level to 80 as fast as possible then Arena or when cata is released I'll do rated bgs.
Only thing they did was nerf all damage from levels 1-79. They wont do much more.