Living at sea full time even surrounded by bright, talented and driven peers comes with many challenges that a start-up probably does not need to deal with (not even addressing the cost issue).
My credentials for saying so: I am a "geek" and a Yachtmaster 200t Ocean Instructor who worked on yachts and sailed across 2 oceans.
On the other hand, using a yacht in a harbour in SF bay, with "crew" on a b1/b2 visa working on startups should be investigated (yet again boats are expensive :P).
watch Fabrice Grinda at TedXParis http://www.youtube.com/watch?v=BJK3_vpfoQc (in French) - implementing ideas taken from one country into another is what he does for a living.
Entrevaux, France - http://en.wikipedia.org/wiki/Entrevaux for something different. Old Vauban fortress in a small village in the southern alps of France.
Not sure I am in a position to give an ADVICE on the matter but the CHOICE I made for my free service is to roll in advertising and affiliation when I have something that add value to the user experience of the service. E.g. I love receiving Amazon's reading recommendations!