It is a good news for you or not?
Few users found it a good news but rest they don't think so...
Google silently announced that it will be crawling the Google Docs Documents, when that document is linked from the web or is embedded to any site.
"This is a very exciting change as your published docs linked to from public websites will reach a much wider audience of people" said by Marie F, a Google Employee on the Google Docs Help Forum.
You have a choice to stop the index of your document. Just keep tour document unpublished by "publishing" it from the "share tab". Google only crawls the document only when your documents in in the web page form and can be dorectly linked to the user without sign in.
So, be careful and keep your document unpublished!!