I had a hell of a scare when I tried the WPAU plugin. It is the Word Press Automatic Update software, maintained here. This blog runs on WordPress, served by Yahoo, a great host, but the version of WP I have is old (2.0.2).
The WPAU software is supposed to first create a WordPress and database backup, then install the newest version of WP (it actually tried to install one version back). It looked like all was well until I tried looking at the site. All my categories were gone, as were my Resume and other pages. Clicking on any link set up an infinite loop, mainly because of the “new and improved” database.
That is, the backup files were corrupted and the database was hosed: certain tables were deleted, others modified. For example, all my comments were gone! Thousands of them. I wept.
But I checked with Yahoo and it turns out that they provide snapshots every four hours (I pay 20 bucks a month for this privilege) and I was able to restore my entire database as of a few hours ago.
All seems well now, and I have a current backup.
So this is a tale of caution. Be careful what you are doing and always—simply always—regularly backup.