<h2>Helping Google find pages not necessarily linked anywhere...</h2>
Interesting discussion at
Webmaster World on how Google might be indexing pages that are otherwise private or hidden from the rest of the world. Ran into this a few times myself when trying to set up a few heavy-load test scripts, only for it to get indexed and get outside hits as well. <_<
Some of the discussion floating around has been centered on the parsing of URLs in gmail messages, as well as indexing pages someone using Chrome or Google toolbar visits.