Ask HN: Not requiring users to sign up

I'm building a website and want to get around the issue of requiring users to sign up/ register with a username + password combo.

A while back I read an article on HN about giving users their own domain for their social accounts and I was wondering if anyone else has implemented anything similar. The alternative is just to use sign in with Facebook / Twitter / Google etc but I want to keep it as simple as possible.

Has anyone implemented something similar?