Invisiblog is a fantastic idea. Completely anonymous blogging, where even they don't know who you are.
invisiblog.com lets you publish a weblog using GPG and the Mixmaster anonymous remailer network. You don't ever have to reveal your identity - not even to us.
Note: there's currently no way for you to edit your content once you put it up there.
One thing it's missing is the ability to download all of your archives in XML or something, in case you ever want to move your content to somewhere else. Though, you could get all your archives and scrape them.
I also question the use of hashes for post-id's. They make for long URLs, and I don't see how they're better than sequential numbers (possibly within the month), or a short timestamp.
The hashes that are used are the hashes of the content. They are used so that content-tampering is obvious. If the content of the post is changed (or the key for the blog is changed), then the hash no longer matches the content and it is obvious that someone or something has changed the content.