The reason? In Maori, 'Wh' is pronounced like an 'F'. So that you understand the problem, say it out loud: Fakatane. Say it again: Fakatane. Do you see the problem? It sounds like 'Fuck-a-tarny'.
So because of some phonetics, an internet filter blocked an entire New Zealand town. Sure, it has now been sorted out, but this is still a great example (and yes, we're talking to you, Conroy) of why internet filters just don't work - 9 times out of 10, they filter out perfectly acceptable stuff.