Search Google for "Steve Souders" and read some of his articles. He is the foremost expert on front-end optimization (and is the guru behind such things as Goog

Search Google for "Steve Souders" and read some of his articles. He is the foremost expert on front-end optimization (and is the guru behind such things as Google's async-loading analytics code). The main problem with the sites that you mention isn't the number of widgets/elements that they load, but how and where they load them. If you want to know more about this, though, you should probably read the relevant threads on StackOverflow.