If you're constantly trying to build the right thing, you have to be constantly willing to reject failed or obsolete ideas to keep moving forward.
Yeah. But, changing your stance every other day is something your engineers wouldn't probably appreciate all that much.
That depends on how engaged your engineers are in the product development process. If they are mere instruments of someone else's vision, no, but if they are also part of the idea creation process, then yes. Facebook constantly deploys and has an experimental mindset towards product development, so it's probably not as obnoxious as it sounds.