Google is not an ad company. People just like to say that because they think it's clever or surprising or something. Google does not produce ads. They sell ad space. So does Facebook. So does NBC. These are product companies selling ad space.
I'm saying the search engine, email, phone OS, and social forums are Google products which are just tangentially related to their advertising business. It would be interesting to know what the real split in revenue is in the discussion about what their real "product" is.