Correct. It's hosted on Posterous and Posterous is down.
Unfunnily, Posterous claims on their Twitter fields to be up.
I feel like this could be terrible press given yesterday - while it's not in any way down to you guys, it definitely won't look good to have two visible downtimes in the space of two days (admittedly, this is just the blog and not other peoples live servers, but it still falls under the same category)