Under normal circumstances using BatchGeocode.com, your data is never stored. In fact your data is sent directly to Yahoo Maps and is never stored anywhere along with the other data in your batch file except in your PC’s memory.
However, when you use the “Save Map to a Web Page” button, we do save your information to a database. Does this mean its on the internet for everyone to see? Not necessarily.
The resulting page is URL identified by a 128 bit 32 character MD5 hash. The Hash is guaranteed to be unique to that map. You can read more about MD5 here: http://en.wikipedia.org/wiki/MD5
The basic skinny of it is though, it would be near impossible for someone to brute force guess the MD5 hash for any URL on our site. Believe me our servers would be dying long before anyone got close with the number of attempts it would take (there are 309,485,009,821,345,068,724,781,056 possible keys.)
We also don’t post these URLs anywhere, if they get picked up by Google or other search engines it must be because you posted it somewhere on the internet.
So, the security of your page is in your own hands. Think of the URL itself as a password.