The problem with these for/against arguments is that they are not mutually exclusive approaches. One one end you have pure web apps, on the other you have pure desktop apps and in-between you have a whole spectrum of hybrid possibilities. As developers, part of our job is to understand the options, what the trade-offs are and how they relate to the particular problem we are trying to solve, and to be able to choose appropriately.
I was going to add a few of my own points but there is so much wrong with the article he was responding to (written by InfoWorld) that there really is no point. Plus the people who visit HackerNews most likely know the pros and cons of on-demand vs on-premise.