According to Yahoo 99% of visitors have JavaScript enabled.
http://developer.yahoo.com/blogs/ydn/many-users-javascript-d...
http://developer.yahoo.com/blogs/ydn/many-users-javascript-d...
This article's audience: software developers
Given that the article is in English as well, and English countries have higher levels of disabled javascript than other countries from that report, and that the target audience is a very specific type of technical focus rather than the general public, I'd hazard that the original point stands.
Not to mention that if some crawlers don't access javascript, you'll serve up nothing to the relevant search index.
I normally browse with it on by default though, but I'll blacklist it for sites that cause my browser to slow down or do other things that are detrimental to the user experience.