That, and extending the scope of search: with mobile their search (and in particular their map search) is far more relevant to brick and mortar advertisers than

That, and extending the scope of search: with mobile their search (and in particular their map search) is far more relevant to brick and mortar advertisers than desktop search alone could ever be. That's a huge market and on top of it on mobile a search user is less picky with the result/suggestion/ad continuum because of the constrained UI. And while most desktop searches are entirely unrelated to monetary transactions and those that are tend to be about spending less or getting more, many mobile searches come quite close to "where can I spend my money". This is where you want to be as an ad medium. The end-game for this is voice UI while driving, where the search provider can basically send physical traffic to the highest bidder.