What The Heck Makes Tumblr a "Designed" Company

I’m asking this question based of a statement made in a popular blog post that was published two weeks ago, Why Tumblr is kicking Posterous’s Ass.

The article from what I can see only references Tumblr as a Designed company because it doesn’t have as many features which for Posterous makes it a bit confusing with all the different things you can use the platform for. It also shows how Tumblr as a nicer and simpler login screen.

But that just doesn’t settle with me completely.

What do you think makes Tumblr a Designed company, and to that regard any more designed than Posterous?