The form for searching out plane tickets and such was the only thing that jumped out at me. It might be a winner if they make it very easy to buy things through the search engine page...eg you search for 'Great New Movie', get a list of cinemas local to your zip, pick the theater+showtime you want, and then get a 'buy' button, all without leaving the search environment.

But things like that have been tried many times before. And I'm sure Google could resurrect Checkout or Wallet or whatever it was called.