However some drawbacks (to compliment the positives of the article):
+ Short Term: While a retreat allows your team to focus and integrate, like all holidays - they end.
+ Talent: You currently recruit in a tech hub city, however eventually your talent leaves and you need to find replacements in the local village. You cannot find anyone as good or as friendly (as they joined the team/party late).
+ Too friendly: You are all new to the place, so you are a little eco system hanging out all the time. The fun will eventually wear off as internal relationships grow/breakdown.
+ Networking: The valley offers fantastic opportunities to meet other like minded people. Opportunities are much higher to meet that next co-founder, angel or VC. What are the chances of this on an island?
So, it can work but not forever and offers startups a constructive way of building strong team dynamics and creating tight focus on building their alpha/beta product.