What if the user uses noscript, or otherwise disable Javascript? Preventing cautious people from seeing the eye candy doesn't sound like a good idea.
(1) It's useless. Just pre-process the style sheets statically. No need for PHP, Ruby or any server side dynamic scripting whatsoever. It's simpler, and yields less requirements for everyone.
(2) It exclude users. Not only the paranoid ones that run noscript and adBlock, but also the ones that just don't have Javascript like Dillo users. (Dillo is interesting for old, weak computers.) That's still a tiny minority, but they do exist.
Something useless that exclude users clearly isn't the best tool for the job. Unless punishing noscript users is a feature… Now, of course javascript is more capable than (pre-processed) CSS alone. But the article didn't seem to use those capabilities.