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.
