Like what? FYI, PDF hasn't been proprietary since 2008, and there are plenty of free/open source implementations of it.
The structure of the specification is gigantic, lengthy, and wrong-headed on many points. It's a file format but it tries to define details of how it should be viewed (!!!). It is bloated and inefficient. It moves things away from becoming efficient data - plain text becomes formatted or even a flat picture of words.
In our discussion of academic papers, Lukeprog argued that lots of smart people preferred to read ideas in academic paper format. Based on my observations, I mostly disagree. But that's just anecdotal evidence. Let's use Science!
Suppose someone at the Singularity Institute thought up a cool new idea: it could be about rationality, Friendly AI, decision theory, making money, or any of the other topics we discuss here on LW. Explaining it takes about ten pages, and it's nontechnical enough that it can be explained to a general audience of non-mathematicians. Which of the following explanations would you be most likely to actually sit down and read through?
EDIT: To state the obvious, this poll will be biased in favor of blog postings, since it's on a blog. However, I still think it'll provide data that's much better than anecdotal guessing. I've emailed a few rationalist mailing lists to try and counteract this effect.