"Yet Google's latest deals contain a hint of weakness. Henry Blodget of Cherry Hill Research, a consultancy, notes that in its original business of placing text advertisements on its own search pages, Google makes profit margins of about 60%. In its more recent business of placing advertisements on web pages belonging to other people, such as bloggers, its profit margins are 10-20%, because it is harder to make the advertisements as relevant to the audience and it must share the resulting revenues. Display advertising also offers lower returns."
Amateur media, like blogs, and professional media, like The Economist, provide great symbiotic context for each other.