Google says their mission is to "Organize the world's information". Great. What does that mean?
It means you catalog and understand relationships in all the world's data. As a side effect, you get a huge amount of attention from all the world's people. People come to rely on augmenting their knowledge and memory with the vast Google repository.
So, if you have all the data, and you have all the eyeballs, what can you do? Simple. You can become the connector between consumer and merchant. You know what people are looking for. You know what others have. For a small fee, you can connect searcher to seller.
Of course they do this today on a small scale - for those searchers that actively look online for products and information. What they don't yet do is reach the people who aren't actively looking. And they don't reach the people who aren't sitting in front of a computer all day.
Slowly but surely Google is going to move their battleship in position to use their:
One way to envision the result is to recall the Tom Cruise movie Minority Report. In the future, you can't go anywhere without being under surveillance, and you are constantly being bombarded by targeted advertising. Video screens everywhere hawk every possible product at the moment you're mostly likely to need it.
Over the next 3 years, that's the direction Google can move in. They'll know what you like, and when you are looking for something, they'll know what's for sale, and they be able to insert targeted ads into all sorts of media - video, audio, 'print', 'online', 'broadcast', etc. Google will also be able to handle the transaction for you.
Note that 'print', 'online' and 'broadcast' are meaningless distinctions within 3 years. Every source of information will be TCP/IP connected: TV, radio, news, movies will all be programmable / customizable.
So as a by-product of organizing all the world's information, Google will change the way advertising works - and they will be the most efficient market for buyers and sellers to reach each other.
At least that's what I'd do if I were them.