$3.2M would be a truckload of money too, but on a Google scale, "This number is really enormous!" is a weak argument. $3.2B is less than 1% of their market cap. Relative terms are much more important than "how many zeros"; why, just recently, Google took a $150M loss in Q3'2012 on the Motorola division. They aren't afraid of 9-figure losses. Thus (IMO) $3.2B being a large number has little bearing on whether or not Google would be willing to take a writedown on Nest, for the right reasons.