In Microsoft Office SharePoint Server (MOSS) 2007 version 12.0.0.6335 (i.e. the December 2008 CU), there appears to be a bug where a scope that only contains Property Query rules is not recognized as having any rules at all (i.e. empty) and therefore is not compiled.

To hack around this bug, add a Web Address rule, as shown below.

Note that in the screenshot above, http://foobar is the Web application that I want to include content from, while excluding the "Pages" libraries themselves from the results (i.e. items where contentclass = STS_List_850). In other words, I want individual pages within the Pages library to appear in the search results -- just not the actual Pages libraries themselves (e.g. the All Items view of the list).

Also note that this is not the exhaustive list of rules required to exclude the various SharePoint items from search results that you most likely don't want to show to users on an Internet-facing MOSS site. I'll defer that to a subsequent post.