Chris Dixon posted on this recently:
Facebook is like a Starbucks where everyone hangs out for hours but almost never buys anything.
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The vast majority of money spent on intent-generating advertising — brand advertising — still happens offline. Eventually this money will have to go where people spend time, which is increasingly online, at sites like Facebook. Somehow Coke, Tide, Nike, Budweiser etc. will have to convince the next generation to buy their mostly commodity products. Expect the online Starbucks of the future to have a lot more – and more effective – ads.
The problem, of course, is that nobody knows how, but we expect someone to figure it out eventually.
So here's a fun question to overcome your status quo bias. What if brand advertising is an artifact of one-to-many communications tech, and can't work in a many-to-many environment?