Perhaps I didn't explain it as well as I could have done (or I don't fully understand Tumblr) but this would be more of an opportunity for people to put out a single post, without needing the full on "their own tumblr". I'm thinking especially people like me (and much of HN I imagine) who don't have the time to put in in maintaining a blog. With Tumblr and Posterous, you never really own the canvas either - I am looking at something whereby you can choose whether you have ads or not or you can pay etc.

Thank you though for your thoughts - it really helps.