Keith Curtis worked at Microsoft for 11 years, coding on Windows, Office, and at Microsoft's research department, before leaving the Redmond giant. Call it a revelation, call it giving in to the devil's temptations, but he's now a complete open source and Linux advocate, and in his new book, "After the Software Wars", he explains why open source will prevail against Microsoft's proprietary model.
Curtis never actually used Linux until 2004, when he left Microsoft. Over the years, he turned into a Linux advocate, and now claims that thanks to the proprietary software model, we are living in "the dark ages of computing." This is what is scientifically known as doing a complete 180 (no, not a 360).