Paul Graham once suggested that startups pose their mission statement as a question. Google's question might have been "Will the PageRank algorithm deliver results that are so good that they lure users away from Altavista?"
via 2010/09/concept.md at master from raganwald's homoiconic - GitHub.
My great lesson from my travel app is that the key question was not "Can you build a decent iPhone app quickly and cost-effectively?" but "Will people look for an app to help their specific travel experience?"
The answer, right now, appears to be "no."