"For the purposes of the poll, a startup can be defined as 'a company working to solve a problem where the solution is not obvious and success is not guaranteed'..."
I don't think there are that many companies, big or small, that are trying to solve problems whose solutions are obvious, and I'm pretty sure that there are no companies whose success is guaranteed.
For example, is it obvious what McDonald's should do to remain profitable in the long term? Should they open more locations or close some of their locations? Should they change their menu? Invest in robots to cook hamburgers? Pay their employees more? Give more independence to their franchisees?
Now ask the same questions about General Electric, which has many major lines of business (jet engines, medical imaging, lighting, etc.). I don't think there are any obvious solutions there either.