[kyrra]

If you do overall page loading times, I wonder what sort of averages you will see comparing this to hosting it locally for all requests.

When hosted locally it would result in 1 less DNS lookup, as well it could reuse an open HTTP connection to fetch the resource.

[crescentfresh]

Correct on both counts. One con of hosting multiple dependencies locally could be that parallelization of downloads is reduced. There's always a flipside and each situation warrants analysis!

So many of these discussion points are discussed at https://developers.google.com/speed/docs/best-practices/rtt

[deelowe]

I think for popular CDNs hosting popular libraries(google's jquery for example), the browser would use the local cache. So, I imagine there's a benefit to using a big CDN for those cases.