Two decades ago, when Google was emerging as an Internet powerhouse, company officials were developing strategies to combat rivals, and eventually landed on a plan to make its search engine the default tool for as many browsers as possible.

In July 2003, Google Chief Economist Hal Varian warned senior executives in an email that Microsoft Corp.’s plan to include web search in its Windows operating system "poses a serious threat,” according to evidence presented Tuesday by the U.S. Justice Department in a high-stakes antitrust trial in Washington. Varian said the company should consider ways of retaining users as it develops new product ideas.

"Up until now we have mostly evaluated those ideas on the basis of technological merit, value to user, and revenue potential,” Varian said in a memo to company executives. While providing a superior product should remain the top consideration, "we should also consider entry barriers, switching costs, and intellectual property when prioritizing products,” he said.