I just tried to search for a bug report that I created a while ago to see if other people having the same issue would be able to find it through a public search engine, but it does not turn up anywhere. Apparently, the robots.txt file blocks all spiders, as per the default Bugzilla setting:

User-agent: *
Allow: /index.cgi
Disallow: /

In my opinion, allowing public search engines to crawl the bug reports could be of a great benefit to people looking for help with a particular bug (and to people who do not like the Bugzilla search engine... ;)). I would propose allowing access to show_bug.cgi and to a page that lists all (at least active) bugs.