alt Hacker NewsIt's telling that basically all of Google's successful projects were either acquisitions or were sponsored directly by the founders (or sometimes, were acquisitions that were directly sponsored by the founders). Those are the only situations where you are immune from the performance review & promotion process.
They've actually had many very successful projects that make the few products and acquisitions you are thinking of work. It's true most of their end products don't work or get abandoned but it stretches their infrastructure in ways that works out well in the long run