To put some numbers to this, lets assume the user has a 1mbit connection with 300ms latency. If a library is 32kb (on the wire) it will take 256ms to transmit

To put some numbers to this, lets assume the user has a 1mbit connection with 300ms latency. If a library is 32kb (on the wire) it will take 256ms to transmit to the client. If its not inlined, it would take 556ms to transmit, or almost twice as long for the cold cache case. If the client has a 10mbit connection (average cheap 4g mobile connection), with the same latency, its even worse as the 32kb library now takes ~27ms to download if inlined and 327ms if not. This is now a order of magnitude slower. With a latency of 100ms (typical home internet), its still 127ms to download the cold cache vs the 27ms inline takes. Since connection bandwidth is slowly rising, it makes CDN library distribution a even worse idea as time passes. The speed of light (in copper/fiber) is the dominating factor in 100ms latency, so it will not be much improved without massive expense. It may even get to the point where inlining the library is faster than waiting for a cheap mobile device to fetch the cached copy out of flash.