Now what if your blog comes down and you haven't backed up the database. Well, you might be screwed...but there might be hope.
Yesterday, I decided to upgrade this really old blog. It's not one that I use a lot and is just a backend thing that I attached to an HTML site for seo reason. The version of wordpress was so old that I had to do a manual update. After the update, however, my site was inaccessible. All of the pointers were pointing to things it could no longer find. The upgrade of wordpress said it was successful, as did the upgrade of the database, but my site was stlll hosed. I forget the the error line exactly, but I copied and pasted the entire error line (other than the site specific parts) into google and there were hundreds of pages generated. Not questions or answers in forums or support sites. Everyone of them was a blog that was down. Hundreds of them.
Now to make a long story short(er) I was able to make a full recovery. I didn't know if it was going to work, but I went to my cpanel and used phpMyAdmin to back up my blog's database, which downloads to your hard drive. I then went to fantastico and deleted my blog, and then created a new one. I then went back into phpMyAdmin and restored my database. When I went back to my blog. It prompted me to update the database to go with the new version of wordpress, and it was as good as new...better actually with all the new WP features the old one was missing.
Here are links on wordpress.org to the steps for using phpMyAdmin to backup and restore your database.
Backing up your database with phpMyAdmin
Restoring your database using phpMyAdmin
Btw, they don't mention it, but it's important that you name the blog folder the same in the new installation of wordpress as it was in the old one, otherwise the pointers will all be off.
Long winded as it may be, I hope it helps. At least, you can't be warned too often to back up your data. have a good day.