On most Stack Exchange sites, jQuery is served from the Google CDN:
On Blog Overflow sites, jQuery is served from the site directly. Not only that, it's served from each
*.blogoverflow.com subdomain directly, instead of from a central location. This means that whenever a user visits a different SE blog, they have to redownload the jQuery script all over again.
For performance reasons, the blog overflow template should be altered to use the Google CDN version of jQuery.