The implementation will definitely need a up to date Public Suffix List. We control a bunch of public suffixes and it's a huge, huge difference if you browse to the address "www.com" or to "com" - or blogger.com and www.blogger.com, or dyndns.org vs. www.dyndns.org. In this case, there are different organizations/persons controlling these.

Should you not know which one you have connected to?