I am grateful to Mark Goodacre for pointing out the existence of a freeware program called Blogger Backup which allows you to make a backup offline copy of your blog. While an accidental deletion might leave a copy at the Internet Archive, if a hacker gets in, they may be able to delete it in such a way that removes it from both Blogger, archive.org and search engine caches permanently.
As with all data, one’s blog deserves the protection of a backup copy. So do the wise thing: Make a backup copy regularly, burn it onto a CD or DVD, and bury it in a fireproof safe at least 6 feet underground in an area that is not prone to floods or earthquakes. Or, if your blog isn’t that important, then just make a backup copy, and keep it somewhere. Or, on the other hand, if you are confident of your blog’s popularity, you can simply assume that your devoted readers have memorized and made copies of your content and hung your words as posters on their walls, which they will send to you in the case of accidental or intentional deletion.