This is not a feature unique to a CDN; the same result could be achieved by simply hosting jQuery on a single server and pointing all your websites to that copy.
My point is that when people talk about using "a CDN", usually what they are really talking about is caching. Whether that caching happens at the origin or the edge makes a very very tiny difference (the lightspeed difference).
My point is that when people talk about using "a CDN", usually what they are really talking about is caching. Whether that caching happens at the origin or the edge makes a very very tiny difference (the lightspeed difference).