Do a search for anything on google, you'll find plenty of urls like:
http://www.undergroundnews.com/ -or-
http://www.undergroundnews.com/test/The search engines read it as an index file and just shove it in their database.
With the current links, the redirect scripts that ship with Threads7 will read all of the SE Friendly options and throw them to your new install without issue (with a meta redirect in place so the search engine updates its links as well).
