I think many people conflate BisDev and Sales too much. Most people in tech have an idea of a Sales guy: the ultimate closer, knows everyone, eats rejection for breakfast. A great sales guy is one of the best assets in a tech startup. That being said, a BizDev person normally is thinking strategically about the company's position as a whole. He is gaining deep knowledge in new verticals and identifying the right companies to target. It's usually a big picture type person. I think the best in this position truly understand the tech involved in the company.