The answer, as always, is moderation and a touch of common sense. If you blog has tens of different widgets on it, that load before the main content loads, then you are exposing yourself to JIL. A couple of external scripts won’t hurt you much, just make sure that they are loaded after your main content. And keep an eye on what your viewers see too. If you notice that a particular script is consistently slow, move on; you’re bound to find someone else offering the same service. If a service is overloaded, this can negatively affect what your viewers see, and reflect badly on your own website.