Awesome, thanks for the detailed response. After reading about CRISPR's natural role in bacteria I was curious if it would have targeting limitations. It sounds like it does (needs GGG triplet), but that in practice this isn't a big deal.

You still need to get this system into a cell -- that's an issue as always, I agree -- but the reduced chance of unwanted mutation seems like a big step forward over retroviruses.

Thanks again for the great write up!