"Amid complaints that things are disappearing from Facebook -- of course they are; Facebook is again in the process of "improving" the site -- there have been admissions that some of you-all don't back up your blogs. Mercy forfend! Back up NOW and regularly thereafter!
I don't know the procedure for all blogs, but here are a couple I do know, and the other services probably have something similar:
BLOGGER: Go to Settings/basic, blog tools and click on “export blog” then click on “download blog” button.
WORDPRESS: Go to Tools (lefthand column in dashboard), click on “export” then click on “download export file” button.
Right now -- backup yer dern blog!"