Which innovative product/service is widely credited with popularizing the modern digital subscription model and proving its viability for physical products in the early 2000s?

In the history of retail and product innovation, subscription models have transformed how consumers access goods and services. This pioneering approach to commerce has deep historical roots but was revolutionized by certain key innovations. Test your knowledge of subscription commerce history and the breakthrough technologies that made today's subscription economy possible.

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Netflix's DVD-by-mail service (1999)
Apple's iTunes Music Store (2003)
Amazon Prime membership program (2005)
Dollar Shave Club's razor subscription (2011)