Back in the day, RedTube had incredibly high quality, low bandwidth video compared to YouTube (which at that stage had been owned by Google for a couple of years). They also had mouse-over previews on the seek bar years before anywhere else did.
Yeah, I often read about porn sites for their engineering (I'm not being sarcastic, I mean that 100% sincerely). It's a shadow world that counts among it some of the most highly-trafficked sites on the internet - and then bear in mind that most of the few sites above them are not devoted to serving high-quality long-duration videos. These sites are phenomenal feats of engineering. Anyone who discounts them just because of some silly pudeur about their content is not an engineer in my eyes.
I don't really see mouseover previews as being in the same league as ethernet, GUI, laser printers, cryptography, TOR, supercomputing, LISP, Ada, etc, etc...
Xerox, under a fat DARPA grant. If you read Kay's "Early History of Smalltalk", or any of the other writeups on PARC projects, it's a genealogy of DARPA projects: