Many do, but as an employee, you should treat them as negotiable. An agreement where the company has default ownership of ideas in the vertical and you have default ownership of everything else is a reasonable compromise that I think most people can agree to. For ideas that are in the vertical, you can ask for permission on a case by case basis. I have this exact system in place and it has worked flawlessly. It requires lots of communication, and a certain amount of trust, but it is much better than the alternative. Personally, I see it as a moral imperative to not sell away exclusive rights to my thoughts.