Have you looked at your raw httpd logs? When I look at mine, and grep away known-cookies, I see that I'm frequently scanned by hundreds of IPs looking for vulnerabilities in common software packages.
And that's just the stuff that shows up in logged HTTP queries. I don't want to think about how likely it is that tools like nessus are constantly being scan-run against IP ranges that I sit within.
Ok, sure, you can believe you're going to be more on top of things keeping your site secure than a high-value target like Google. I don't know how the target value of your site, but I doubt it's as high as the server the jQuery plugin you're afraid of pulling remotely sits on--and you can bet that Google knows they have high-target-value externally-facing assets, and are watching them even harder and with more eyes than you would.