I think a lot of people here take offense at the tone of this article (a tad bit condescending and patronizing) and rightly so. However I think people are missing the bigger point of the article which is to serve as a reminder that there are bigger(other?) problems to solve, and it would be prudent to make a case for the other causes the author mentions. Think of it as a pitch to the next generation of entrepreneurs. (Yo knocked its pitch out the park with its million dollar funding and news headlines).
I do not agree with his target audience, since the bigger problems are big because of their difficulty. If they were problems that could be solved with little effort/limited finances they would have been. (energy, food, water, health, education). Apps such as Yo exist because they can obtain funding to the tune of a million dollars. His pitch should be to investors to invest wisely keeping in mind their social responsibility and make a case for the importance of these other big ticket problems as opposed to apps like Yo. It does not make sense to berate engineers/start up founders etc. for their chosen path especially since they do not own the capital required to solve "smaller" (acc. to the author) problem let alone a "big" world changing one. They are almost entirely reliant on working up to their next round of funding.