If you have been wondering why certain protected posts just straight-up disappeared from this site and the RSS feed, the reason is that I started using the ViewLevel plugin to protect posts. Since I removed the passwords that were formerly protecting the posts, if anything happens to the plugin (i.e. it suddenly stops working), the protected posts would be exposed. As a result, I am a bit wary about upgrading to WordPress 2.0, which will be released on Boxing Day (December 26). Owen's comments on the matter are somewhat funny:

If you are running a "view level" plugin - something that restricts a reader's permissions to access certain posts - I'll say straight out right now that unless you've got a brand new version (and I know of no author who has written one of these plugins that is offering an updated version) it's not going to work. If you have an update, comment here - I'm looking for it myself.

Luckily, there is no compelling security reason to switch immediately. I will probably wait a bit to see whether ViewLevel is updated (and also to see if upgrading problems cause WordPress 2.0.1 is released). Since I am getting a bit tired of the way this site looks, I may attempt to find a new theme to use.