It isn't so simple, because what makes google (and facebook in its own ecosystem) so valuable are all the data they gathered about you. If you make ads context-

It isn't so simple, because what makes google (and facebook in its own ecosystem) so valuable are all the data they gathered about you. If you make ads context-sensitive, google is not bringing anything better on the table than any startup in that domain could bring, maybe some minor cost optimization due to scale. But they can sell customized ads stating that they will be very well targeted regardless of current content. Which seems to be what advertisers want much more, and reason why facebook never opened up their apis to google+ IIRC, your social graph and its use is basically the only worthy thing on whole facebook. It of course brings all this tracking evil, why google stopped being morally OK company etc. But the money are there.