I would add three others:
1. Spending too much time designing an "About" page, a "Who we are" page, an "FAQ" page, to present the startup and what the product will be, rather than actually developing the product.
2. Being very secretive about your very great (but generally vague) startup idea, instead of working on execution.
3. Having a product that is perpetually "almost ready" to launch but never getting around to taking care of that last 80%.