With Googles CDN, they have to hack either my website, or Googles CDN.
Whichever you choose, it wont make any difference to how quickly you notice a local hack. Increasing the attack space doesn't make you more secure.
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.
You implied that the security cost for hosting on your server was actually lower, because you weren't as much of a target. My reply was an attempt to point out to you at a technical level why that was a specious argument; your servers are likely being scanned by the same botnets that are scanning mine with automated exploit attempts against old and vulnerable software, and common errors in securing a server.
It's going to be far easier and cheaper for them to take a shotgun-scanner approach against a large class of average systems than to apply manual, concerted effort against a small set of high-value targets like CDN nodes.
The cost to the attacker to attack your system with automated tools is near nil. They'll attack, and if they get in, that's gravy. Using "we're not a target" as a security model makes about as much sense as putting an unpatched Windows box in your home router's DMZ.
We're only talking about moving one of my files from my current website to an entirely different third party service over which I have no control...
Do you not understand this? Spreading my website over multiple services controlled by multiple people decreases the security... Obviously...
With that misunderstanding corrected, I believe you're generally correct on the security argument. There's still some plausible variation in terms of server security policy and implementation of things like intrusion detection, (Is it safer to keep all your money in your home, or is it safer to keep most of it in a safe deposit box in a bank?) but that's not the key problem I thought I noticed in your argument, and not one worth devoting energy into.