When working with people of the same industry on a joint project, for example to make a bigger pie, you have to be careful not to share too many secrets, of course, but also not to share too many of the same ideas. If you end up copying each other, which is fine for a while, you stop competing against one another as fiercely as you could be, and this affects the innovations that affect the industry as a whole. Best to always have some competition, some part of the pie to take. By all means make it bigger, but keep the competition alive!