As he mentions in the post, this is from one of the creators of Tumblr, who's elevator pitch at this point is "a social network that gives users control of their identity". It is one of the easiest ways for someone to practice what he's preaching. Still, the people who are converting everything over to Google+ aren't crazy (well, they are a little bit, no search and no RSS is kinda a big deal). The design of G+, part…
Also worth noting, he's no longer using Tumblr for Marco.org: http://www.marco.org/secondcrack
"Custom domains
Use your own domain name.
Turn marco.tumblr.com into www.marco.org"