This excerpt originally appeared in C-Net on August 13, 2012.

Eli Dourado, a research fellow at the Mercatus Center at George Mason University, argues that "duopoly can be consistent with vigorous competition." He uses the digital camera market as an example. Nikon and Canon are the only two major players selling DSLRs on the market. And "despite the dominance of these two firms, the price of DSLRs falls every year, and quality continuously goes up."