Closure probably fell out of vogue because it's excellent, but written in java.

Closure fell out of vogue because it's fairly heavy and seriously subsets javascript, which makes it convenient when you're compiling to javascript (from a very different language, not just augmenting/macroing it), but not when you're writing it by hand.

Something interesting is that I believe Google is working on a compiler that converts TypeScript to Closure, which would let you take advantage of the closure compiler while utilizing TS. That would be a very exciting development.

That's interesting. Are there any mailing list posts, issue links, etc. you're aware of that cover some details?