It's try to buy, and if that fails, try to compete. At Google's size, it would be very, very, very difficult to spread their peanut butter too thin, and their Superbowl Ad indicates that they are focusing on what everyone knows them best for and only dipping their feet into other pools that they can't buy into.
Their main focus is search and adwords ...and more recently snooping dns.
Now instead of letting facebook do their thing and google offering competitive ads, they choose to do facebook thing.
Now what? They are going to clone all the sites that their users spend more than 15minutes on?
They`re going to spread their peanut butter too thin.