Google does both heuristically parse Javascript and execute Javascript, for at least some fraction of their crawl. This is obviously much more expensive than doing HTML parsing, particularly once the Internet largely goes from static HTML to AJAXy magic.
Granted, but if Google can't parse it, I highly doubt anyone else is going to. And as nice as it would be if every web developer read the "Google Guide to Being Nice to Our Web Crawlers", as an internet we still can't get away from IE6. The term "pipe dream" comes to mind.
