If I understand the article's point, essentially, carriers pay for the egress traffic that causes DDoSes, that cost and the cost of the generated ill-will outweighs that of filtering, whose price has fallen and continues to fall.
Personally, I think that if the article author is correct, then I wonder if this is one of those high-level long-term decisions that companies appear absolutely incapable of making. (In my experience, short-term gains are way overvalued at the cost of long-term loss, generally, especially when it is hard to directly determine the costs/benefits involved.)
