This was eluded to in Kara Swisher’s aforelinked piece but it wasn’t spelled out quite as well as this, by Nicolas Carlson at Business Insider:
Mayer’s rule: If a new product can’t be shipped in six months, and if it doesn’t have a realistic shot of reaching 100 million users or generate $100 million toward the company’s top line, then Yahoo will no longer bother.
I don’t know if I agree with her rules but I really, really like that she has some.
(This is the longest title to a post on my site. I like the rules that much.)