While I would agree with the OP that a lot of these projects target the needs of large, FB-like companies, Reactjs and Flux (Flux is a pseudo-framework for React) are really nice alternatives to heavier options like Angular and Backbone. If you're building with JS on the front end then definitely take a look; the speed advantage over Angular is ridiculous.
2 clarifications for the summary, since I was the 10th engineer at MP3.com and worked there from 1999-2003:
- We lost to the record labels/publishers not because we gave people access to their music, but because we compiled the music library and streamed it without paying the labels/publishers any royalties. Our strategy was to buy a copy of the CD ourselves, rip it, then claim fair use doctrine when we streamed it to someone else who also owned it. This was a supposed grey area in the law that got cleared up REAL FAST in a media-friendly district court. Services that you see now are paying royalties on what they stream. MP3.com later sued its lawyers that gave the advice on the so-called "grey area" it tried to go through.
- We where not a Silicon Valley company, we where in San Diego. Perhaps if we where SV we would of gotten better legal advice
NFL2k did look amazingly awesome at the time. I remember standing in a mall watching the computer play itself, Eagles vs Rams. The Rams threw for a touchdown and the guy standing next to me turns and with a straight face says, "I didn't think the Rams would pull that out". To this day I don't know if the guy thought he was watching a real game or not.