I have just finished reading Scott McKain's book "Collapse of Distinction". It does a good job of describing competitive emulation.
Company A invents a truly unique product or service and establishes itself as a leader in the market. Company B, seeing Company A's success, enters the market and introduces a similar product. Now the emulation cycle begins. Company A starts developing its product in a way that not only serves its customers, but also competes feature to feature with Company B's offerings. Company B responds similarly.