I've never used web workers, but as a developer who has written a lot of multi-threaded code in C++, I'm kind of glad that as a user I don't have to suffer poorly written non-thread-safe JavaScript. I've seen some terrible multi-threaded code by developers who just didn't get it. I suppose that's why web workers are designed the way they are: to make it easier for developers who maybe don't quite get the intricacies of multi-threading.