Okay, my experience is limited to one big company, but I found I rarely need to ask permission to do anything but launch. And that's only because launching instantly means more people will be using my product than most startups get in their lifetime. I'm perfectly free to build stuff, show it to friends (as long as the friends work within the company), improve it, make my own design calls, etc.
In fact, I'm encouraged to do so. When I joined, my boss said "If you see something that's broken, just go fix it and mail off a codereview". He's since told me "If you have an idea, just go ahead and implement it, don't even ask my permission." And when I've done so, the reaction has generally been quite positive - I got a free phone out of it, after all.