I'm too much a dummy when it comes to technology and computers, but from what I understand he can apply robots.txt right now and wayback machine will delete the archived versions of his site they've created. From what I gather it's very easy to remove stuff from wayback machine, which is why I use archive.is to backup wayback machine webpages that I'd like to preserve. Unlike wayback machine, it is much harder to remove stuff from archive.is. Seeing that Jake's site has been archived through archive.is, I'd say that not using robots.txt is the least of his problem.