[jol]

you are right about first, but >- at least as reliable as your infrastructure this doesn't mean that Google CDN is down the same times that your server is, thus it adds downtime (or time when something is broken in the site), i.e. if your server doesn't work, nothing works, if your server works but CDN doesn't, again something is broken and if this time doesn't overlap, it is just additional risk, even if tiny one. Also, what happens when Google decides to charge for use of the CDN?

[estel]

Ignoring the last point, this is probably why the HTML5BP loads from the CDN but fallsback to a local version if the CDN can't be reached.

[nucleardog]

It's fairly trivial to load jQuery/other libraries from the Google CDN and fall back to a local copy if it fails as long as you're not using async/deferred.

We've got it baked into our boilerplate.

If Google decides to charge for use of their CDN, then I wish them luck. They don't have any billing information and short of serving a bastardized jQuery (simply not serving it will trigger the fallback) our projects will continue as they've always been.