It's easy for the spike in demand to have bad environmental consequences (e.g., biodiesel, Fiji water), or economic consequences for people who depend on the crop as a staple (e.g., quinoa). And this would certainly be a factor in whether I will buy the product.
But this doesn't seem to be the case (yet) with coconut water: http://www.motherjones.com/blue-marble/2010/07/coconut-water...
I visited Kerala several years ago, and I have to say the life of a coconut farmer there seemed to have its advantages. They spent their days tending their carefully cultivated trees just a couple hundred meters from a beautiful coastline.
P.S. We also drink a lot of sugar cane juice here, with ice and a bit of lime squeezed in it. I like it even better. Maybe it will be a fad in some 5 or 10 years, though it's sugar content is (obviously) quite high, and I don't think it keeps as well as coconut water. Give it a try if you're ever in Little Havana in FL.
Also supporting hundreds of millions of sales and preserving the same quality is a problem; as someone noted the stuff they sell here it's ridden with sugar and preservatives. I'm sure it's not as tasty and healthy as your grandma's backyard stuff.
Many just need a hug and some emotional counselling.