Yahoo adopted Scrum in 2004 with one experimental team and gradually expanded to over 200 Scrum teams by 2008 with over 1500 employees. Key results included an average team velocity increase of 35% per year, development cost reductions of over $1 million per year, and a 100% return on investment in trainings in the first year. While 15-20% of employees did not like Scrum initially, Yahoo saw faster time to market, higher quality, and satisfied customers compared to waterfall.