I'm not yet sold on the perfect substitutability of backups, but the point, while interesting, is quite irrelevant in this context. If backups aren't perfect substitutes, they won't affect people's behaviour. If they are, then increased risk is essentially immaterial. If I don't care about my mortality because I can be easily resurrected, then the fundamental value of me taking risks changes, thus, the fact that I take more risks is not a bad thing.

Now, there may be a problem that people are less concerned with other people's lives, because, since those people are backed up, they are expendable. The implications there are a bit more complex, and that issue may result in problems, though such is not necessarily the case.