At what point is a GMail plugin able to transform itself into a startup like Rapportive? A to-do list probably don't have a very big chance of changing the world, but a better one has the potential to impact a small subset of people who feel the same pain points as the founders. Probably not startup worthy, but the main point of a startup is really to take a problem and find a solution to it, and if these kids are addressing a real problem and making a calculated shot at a solution, then why not?