[fh973]

It probably sounds odd, but I think Google is not good at doing large complex projects that require considerable man power and time.

And that's what you need to refine products to the next level (or go into billion dollar markets).

It's partially due to the promotion system, partially due to bring allergic to top down management, paired with some arrogance.

Best example are their numerous failed attempts to do payments. Apart from search and ads (which have strong leadership) the examples are legion.