Its not only Google that can crawl and index the pages other search engines can do that as well. Here is a extract from Google blog post
Allow published docs that are linked to from a public Web site to be crawled and indexed, which means they can appear in search results you see on Google.com and other search engines
Now the big question, how do I protect my documents from being searched?
- You will have to choose the option ‘Allow anyone with the link to view’
How to make Google and other search engines, give search results from my Google doc?
- A Goole doc needs needs to be explicitly published using the ‘Publish as Web page’ or ‘Publish/embed’ option and which are linked to from a publicly crawled Web page.
Google is very excited about this as it has said in its Blog post; “This is a very exciting change, as your published docs linked to from public Web sites will reach a much wider audience of people”. Want to read more? visit the Google’s blog post.
By the way Google is excited, are you?