Facebook founder Mark Zuckerberg thinks that people on the Web don’t need privacy anymore – that the very principles on which Facebook was built – you only share with a trusted group of people and no one else has access to what you say – are outdated.

The argument is that whether we like it or not, the world is moving towards less privacy and more sharing. People are starting websites, blogs and Twitter accounts, where they’re sharing in ways that they had never done before (some would say over-sharing).

All of this is inevitable and Facebook, by adjusting its privacy settings to make its default public rather than private (and giving users the option to reinstate some privacy protections), is now joining the trend. No big deal, says Zuckerberg.

Personally, I’m not exactly shocked. I never trusted Facebook to keep my information private. I always assumed that whatever I post there can be seen by anyone and have acted accordingly.

But I know many people who see Facebook as a great way to keep in touch with family and friends. They do post intimate details about their lives on Facebook, and photos of their kids. They don’t see Facebook as the World Wide Web but as a closed community of users; they don’t filter what they say over there because they trust that only their friends would be able to see what they say. And making it all public unless they take action ans make it private again (and they can’t even make all of it private now) is not what they had in mind when they joined Facebook.

Most likely, Facebook is giving up privacy not so much because it thinks people don’t want it, or need it, anymore, but as a reaction to the very public Twitter. I guess Zuckerberg worries that keeping Facebook a place for people to privately interact with friends will eventually be too limiting and will stunt its growth.

In a way, making Facebook public IS the end of privacy. It’s a breach of confidence on some level, and I think it means that going forward, people will have a hard time trusting any social network that says it’s “secure.” I don’t think it’s a bad thing: I think that whatever we put on the Web, anywhere, we need to assume that anyone would be able to see it. Maybe it’s the end of privacy. Maybe there was never real privacy on the Web.