Hosting jquery on your website increases the load on your website, this increasing the probability that your website will fail. The more sites that use the CDN

Hosting jquery on your website increases the load on your website, this increasing the probability that your website will fail. The more sites that use the CDN, the more likely someone coming to your site already has jquery in their cache. If you're just trying to minimize downtime, regardless of cost then I absolutely agree with your analysis. However if you're trying to minimize something more complex involving downtime and cost, then maybe there's a point where it makes sense to use the CDN. Something very high volume like Twitter, for example.