I think it depends what you're after. Building something brand new is more interesting and challenging, but taking a proven design and introducing it to an untapped market has a higher probability of resulting in "something people use", for substantially less effort. So I disagree with the "I have nothing better I can do" sentiment.
> That's the essence of a startup: having brilliant people do work that's beneath them.... Think Einstein designing refrigerators.
The idea being that once you've made your pile, you can go on to do more interesting things, like novel startup generator startups, or writing your own toenail clippings and oatmeal language, or whatever else you fancy:-)
