It's much more than that. When people use a CDN for their applications, they want to be 100% (or 1000% if that were possible) sure that the CDN will not be compromised. They also want to be sure that the people running the CDN do not have nefarious intentions. They also want 100% uptime. They also want the CDN to stick around as long as their web app is around.

That's why CDN's from Microsoft, Google, and the official jQuery CDN's are trusted (and will inevitably be trusted) more than this one.

As awesome as this is, I'd quite honestly rather host my JS myself than use it. Once Google adds more libraries, I may use their CDN.

EDIT: I don't mean to come off too harsh, but a lot of people don't use CDN's altogether because of the potential for downtime. Combine that with a not-globally-recognized brand and it may not work too well.