I use Google Scholar and find it useful to receive notifications about citations to papers that I was a co-author on. A lot of these notifications concern papers that have been formally published in a journal. Sometimes though, Google Scholar finds things that are just out there on the web and are in the process of being published.
Today I received notification of a paper that cites some work I was involved in. The paper was a Word Document, that was inside a zip archive, that was on an FTP site of a very-famous-mutinational-software-company!
The zip file includes all of the files that will accompany the manuscript submission, including the cover letter. I'm really not sure if this was intended to be public yet so I won't provide any specific details. Hopefully the authors remembered to turn off track changes so that people can't see the history of all of their edits. I guess the lesson here is to be careful about what you leave on your web or FTP site...Google will find it!
Update: I decided to email the lead author to let them know that their manuscript may be a little more public than they had intended. It turns out that they were not aware that the manuscript had been indexed by Google Scholar, so I assume they'll be removing the files from their FTP site (though at this point many of the details of the paper will remain in Google's search indexes).