Сайт blog.jquery.com сообщает:
Lately, we have noticed a significant increase in traffic from sites that hotlink directly to files on our various properties (jquery.com, jqueryui.com, dev.jquery.com, etc.) instead of downloading and hosting them locally or taking advantage of the CDNs that we and others (Google, Microsoft, etc.) provide for this purpose. This behavior has started to negatively affect the performance of our network and is preventing legitimate users from accessing our site at peak times.
In order to improve the performance and availability of our sites for all users, we have disabled hotlinking to images across our entire network. We will be disabling hotlinking to all other types of content (such as CSS and JavaScript) at the end of January. If your site is hotlinking to jQuery domains other than code.jquery.com, please be aware that you must update your site before this deadline or it will stop functioning normally.
Таким образом, c 31 января нельзя будет брать jQuery с сайтов типа query.com, jqueryui.com, dev.jquery.com и т.д. Все хотлинки на такие сайты, кроме code.jquery.com, будут резаться. Так что пользуйтесь CDN, например Google CDN или Miscrosoft CDN.
Ссылки по теме: О CDN, Особенности Google CDN