Come on, man. 5 year old data? 20-30% of top websites are currently using Google's CDN, so it seems like you're wrong about the picture not having improved significantly. You really think people don't have DNS for ajax.googleapis.com already? And HTTPS is available (and default), so you really think somebody is gonna hack Google to serve you bad JS? You also conveniently ignore the benefits of domain sharding and the fact that the CDN will serve the files faster and with lower latency than almost any setup. And that HTTP/2 mitigates the cost of not concatenating your scripts.