This is called DNS Hijacking and it's very annoying.
As a programmer, I rely on receiving error messages when appropriate and being able to do the right thing in response. These days a lot of software works by sending HTTP requests and if these requests, to perhaps an internal domain, succeed when really they should fail all sorts of bad things can happen.
One solution is to use Google's new public DNS.
Dear Bigpond, please don't mess with my internet connection, or at least let me know about the setting and allow me to opt in or out as I wish.