This topic opens the door to a lot of subjectivity. Here's my2 cents on the matter: it's more a question of how deep should that technical knowledge be. A successfull product manager needs depth of knowledge in areas such as business processes or the industry. On the other hand, the technical knowledge is important to smoothen communication with the developers working on the product. So even shallow knowledge could get the job done. The point being that technical knowledge isn't a game breaker.
