you're right in that I should have checked first, and really if you think about it it's no surprise that YouTube, Yahoo, Google etc are using their own tools. That does not detract from the point that jQuery has massive, ridiculous mind share and completely dominates the web though. Your point about it being impossible to build a gmail style app in jQuery is extremely dubious. There are an awful lot of complicated JS apps built on jQuery.
If you check you are right. Amazon, eBay, and MSN all use jQuery. (at least on their homepage).
You can't simply look for the global `$` or a single file named jquery.
I work on large corporate applications and we use jQuery, but we would fail the `$` and jquery file test. We don't expose the global `$` and jquery gets combined and minified with our own code.
You seriously underestimate the complexity of Gmail. It may well be the most complex JavaScript application in existence with an appreciable user base.
You make a fair argument. Google has several state-of-the-art JS applications. I thought of Gmail in particular because it probably sees much higher demand and so matters of optimization are probably a bit more important to it. This makes the amount of network activity, client-side caching, etc. it manages really impressive.
But no doubts that Google Docs is in the same ballpark.
