Optica Tumblr Theme: http://www.tumblr.com/theme/37310

Example 1: http://blog.k-create.com/ (the creator of the theme i believe)

Example 2: http://teslachat.tumblr.com/ (i work here)

Example 3: http://nerdydata.tumblr.com/post/57308630996/how-we-found-all-of-optimizleys-clients (just saw this on HN)