I'm in the very early stage of a creation of a startup focused on online file sharing for companies: the idea is to do something like sharefile.com or smartfile.com but in France. So I know that there's a market with established competitors (also a few ones in France). I still can't decide whether doing early customer discovery, testing hypotheses etc is a good idea or whether I should spend time on building a product instead. I'm not sure whether customer development methodology applies for an existing market with existing competitors.