I started moving away from YUI between v2 and v3, mostly because the project started feeling very disorganized. There wasn't a clear timeline as to when components from v2 would be upgraded to v3. Namespacing helped, but I didn't want to invest time developing code around v2 components if v3 versions were right around the corner, but there was little to no insight as to if/when components would be migrated.

That seems to mirror the rest of Yahoo from what I've seen - some really good/cool/useful tech, poor management/communication about it. Perhaps at that size, it's just endemic in a culture?

You make some decent points, but a guy like Doug can work wherever he wants so while Yahoo! might release more open source packages than 99% of the shops out there, you can't just throw out the other, better companies in the top 1% like Google and Twitter who, in my opinion, release much better open source software, software that I actually use. I agree that Yahoo! has over the years done a respectable job in becoming a leader in open source JavaScript development, but since Doug has had a huge hand in this, couldn't one argue that he could bring that along with him wherever he goes? Furthermore, in some of these other companies, at least his CEO won't be just pretending to know what JSON is :)