jQuery is great. It’s cross-browser, easy to learn, and makes adding interactivity to your website a breeze. It also comes with plenty of plugins to do almost whatever you need it to do.

So there are lot of benefits from loading  jQuery from popular hostnames or sites (For Eg. Google Hosted Libraries).

Here are the most popular sites across web:

Sites/Hostnames Percentage of sites
ajax.googleapis.com 18.30%
code.jquery.com 1.40%
yandex.st 0.30%
ajax.aspnetcdn.com 0.20%
mat1.gtimg.com 0.20%
ak2.imgaft.com 0.10%
img1.imgsmail.ru 0.10%
http://www.yfum.com 0.10%
img.sedoparking.com 0.10%
http://www.biggerclicks.com 0.10%