I maybe missed this detail in the book, but why would a very rich person with scheduled needlecast backups of their stacks not have multiple historical versions of them stored, just in case a virus crapped all over their most recent save? In fact, if a rich person had an alarm that told them when a virus had infected them (which they apparently do in the book), then all you would really ever need to keep is two copies -- the most recent one, and the one before that. Then, even if you were too late to stop an inopportune, infected update, you would at least know well in advance to fix it before the next update, and you could just use your second-oldest backup. Is storage space really that expensive in the future? (It's certainly the cheapest part of technology these days).