The hacker pool is the place where hackers end up in if they modify game code to create an unfair advantage. So anyone in the hacker pool will only battle against hackers.
This is probably the more win-win choice than the conventional method of banning them all together. So while hackers can still play the game without disrupting the non-hacker majority, the minority hacker community can still contribute to insane views on YouTube or other video-hosting sites, which in turn can still bring the Ninja Kiwi company some money.
I suppose other companies don't do this "hacker pool" stuff, but I suppose it is a nice idea if the company has a good video-hosting base.