Not a Google fanboy by any means, but couldn't this be read with the opposite conclusion as well - that the average time that Google keeps marginal products alive is 4 years?
Of course it's possible that everyone has some personal favourites amongst those 164, but if an idea really has legs what's to stop people from exhuming it from the Google graveyard?
Of course it's possible that everyone has some personal favourites amongst those 164, but if an idea really has legs what's to stop people from exhuming it from the Google graveyard?