http://forums.dds6qkxpwdeubwucdiaord2xgbbeyds25rbsgr73tbfpqpt4a6vjwsyd.onion/t/onion-services-authentication/975
This information becomes sequestered in search crawlers allowing anyone to try and connect and probe your Hidden Server even if this wasn't your intention.
To set up a Hidden service in a private mode, only accessible by just you or additionally your trusted associates, there is a little known feature in Tor feature known as Onion Services Authentication.