Last year when I was working on an enterprise search project with SPS 2003, I was frustrating on getting the rules that include or exclude content from content index work. I called Microsoft and I spent 3 hours with a Microsoft guy on the phone but got nothing useful.
After many hours testing by myself, I found the order or the include/exclude rules in a content index is very important and effects your search result enormously (But MS told us this doesn't matter.). I guest it is because each time when the search engine will index an URL, it first tests this URL against all rules one by one, and when it reaches the first satisfied rule, on matter it is an inclusion or exclusion rule, it returns immediately and ignores all following rules. For instance,
exclude: http://server/abc/def/* ---- not working because the inclusion rule on top run first and block this exlcusion rule.