Find sites sharing the same IP address
sharingmyip.com
sharingmyip.com
Basically it will only show sub-domains within the domain you search for, unless previous searches for other domains happen to match the IP.
I tested this just to confirm: I searched for one of my domains (apr. 20 domains on the same IP) and only sub-domains showed up. I searched for another of my domains and the sub-domains+my previous search showed up.
But I think you are bypassing the point here somewhat. The point isn't that it only relies on previous searches, or on previous searches at all. The point is that it is not, and will probably never be a complete database, at least not the way things work as of now.
Just for fun I tried a couple of other tools that boast the same feature (http://spyonweb.com and http://www.yougetsignal.com/tools/web-sites-on-web-server/) and they both found most of all of these sites without any problem.
The major difference here is your site has a nice clean interface with a very easily parseable source, something these two other sites definitely don't have.
Now, if you could manage the same results as these other sites maintaining the clean interface you have now, it would definitely be my future choice. But as long as there are other sites out there that provide more reliable results...
I suspect this site uses Bing under the hood - finds the IP of entered website domain, queries bing and returns the results.
This is widely used by security folks when doing pen testing - even if you don't find any flaws on the targeted website, there's a great chance other websites won't be as secure if it's on shared hosting and such tools help to find those other websites.
http://sharingmyip.com/?site=ycombinator.com
It finds related sub-domains being used, like wiki.ycombinator.com
Or for Cisco: http://sharingmyip.com/?site=cisco.com
It shows that some of their external domains are pointed to internal addresses (in the 10.0 range).
I used to work at one of the major CDNs, and we spent a lot of effort segregating some of our customers into separate IP space, so they wouldn't cause the rest of our customers to get firewalled by the likes of China.
Also owns iblog. com, tablets. com, etc.
http://sharingmyip.com/?site=facebook.com
They have dev . facebook.com pointing to 10.30.0.50 (internal IP address).
Yup www.kymalabs.com brought back a couple pages.
I can see some spammy looking sites on the same ip as a small site I set up for a friend.
Should I be worried?
That's quite better than fail actually, it understands that the user is trying to test me :), in turn it benefits.
But definitely no results for first timers. Multiple sources (gps, wifi) could be used to build out a cell-id -> location DB in similar way.