This doesn’t mean your documents will be shared with everyone. Rather Google is notifying their users that only publicly shared items will be indexed. Users should double check on any publicly shared items to make sure that they really should be public (here’s how).
While on the surface this may seem like an invasion of privacy, and it might be if you haven’t taken care to make sure you have not shared sensitive items, it also could be a great way for web visitors to search and find your site.
Imagine if you publicly publish a list of tips and tricks for a product that you work. By linking to this public document you’re telling Google that it’s ok for a user to find the document in a search. Which in this case is exactly what you want.
Rather than be concerned by this as a privacy issue I think everyone should focus on the search potential.
Increasingly potential customers are doing very specific keyword searches on the web. The more links you have from different areas the more likely they are to see you as an authority on the subject matter.
The higher your perceived authority — the less competition that you’ll have
Used smartly, these shared public documents could be another effective way to reach potential clients who increasingly are searching for help on support issues prior to calling in the consultant. The more (free) ways that a potential client can find you – the better!