In the last week, I checked most of my sites of the broken links. The link point to the web page which is not existing any more. It may return 404 error, or redirect to a domain parking page. There are about 500 broken links in one of my sites.
I have a WPMU installation used for years. One MU plugin I use is Ada WPMU Sitewide Feed. Until WordPress upgrade to 3.0. It has multi-site support internally. So, upgrade WPMU to WP 3.0.1. The problem just found that Sitewide feed does not work any more. No content in the