We tried selling our product to users but that failed miserably; so, we turned to an ad-driven model. The way it works is, we give away the product for free, then lure advertisers with the promise of connecting them to millions of people who hate to pay for things. Amazingly, it works.

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Ryan Chittum is a former Wall Street Journal reporter, and deputy editor of The Audit, CJR's business section. If you see notable business journalism, give him a heads-up at rc2538@columbia.edu. Follow him on Twitter at @ryanchittum.