 Although recently developed in terms of economic theory, two-sided networks help to explain many classic battles, for example, Betamax vs. VHS, Mac vs. Windows, CBS vs. RCA in color TV, American Express vs. Visa, and more recently Blu-ray vs. HD DVD.In the case of color TV, CBS and RCA offered rival formats but initially neither gained market traction.Viewers had little reason to buy expensive color TVs in the absence of color programming.