You do realize that the power of Cas9 is not it's ability to cut or even induce non-homologous-end-joining, but rather to co-localize with an exact sequence of

You do realize that the power of Cas9 is not it's ability to cut or even induce non-homologous-end-joining, but rather to co-localize with an exact sequence of DNA (that can be changed in a day for a few dollars). Cutting DNA is certainly a great self-defense mechanism used by the bacteria that causes strep throat to attack other bacteria. But in the ways that Cas9 will eventually be used, likely its entire endonuclease activity will be stripped, leaving only its homing ability. And for that you can swap in any other useful protein functions that now happen at a particular sequence location. And that is what makes Cas9 so exciting. That NHEJ works at all is just a bonus to get us to some early results quickly. fCas9 or dCas9, or a nickase (different endonuclease, and endonuclease-dead respectively) as well as a host of other variants actually hold great promise precisely and solely in their ability to locate a sequence.