I currently have a new site under development and I brought it live last week for the purpose of testing and development. It is filled with content, but since I'm still working on it in a sandbox, I have the follow robots.txt:
Nobody should know about this site and I do admit, I had the toolbar activated for a while when testing.
Either way, I noticed that Googlebot has been crawling the site and now has 5,010 pages from the site live in the search results!
Baidu and Yandex somehow also know about the site but neither have it in their respective indexes.
Since I don't plan on creating a webmaster tools account, how the heck can I prevent Google from trespassing?