I've switched from wordpress to posterous to tumblr. I like Tumblr's lack of branded drop down button that Posterous has even on self hosted, custom themes. Photographer Terry's Diary is a minimal Tumblr powered blog thats pretty interesting - http://www.terrysdiary.com (mildly NSFW)
Wait - I see two buttons on all Tumblr sites: one that says "+ Follow" and one that says "Join Tumblr". Is this something that I'm in a bucket test on or does it go away if you're logged or something?
I don't think they ever directly called Tumblr a dying platform. The dig seemed aimed more towards Ning, which was the first platform they supported, and could reasonably be called dying for people who want a free blogging platform, as could several of the other platforms.
The HN comments about the campaign seem to do more to further a catfight than the original blog post did in the first place.
I think behind all this competition from the blogging platforms there is a realisation that at the core their offerings are quiet similar because of the nature of blogging.
It certainly isn't a internet startup area where there is going to be to much innovation given that to many features and you lose the people wanting a simple solution and end up competing with self hosted wordpress for more serious bloggers.
