Of course, the article manages to overlook the one very good, very technical reason for ad-blocking: many of those ads are doing a lot more than simply trying to get you to buy a product immediately. A large fraction of them are essentially low-grade spyware, using various techniques to assemble a profile of who you are and what you are interested in, by tracking you across many websites. That profile is the main reason why advertising online is worth money, and why page views matter every bit as much as clicks -- the spyware takes effect when you view the page.
But that said, the original point is a valid one: these sites need to make money somehow. And the shareware principle is very deeply embedded in my soul: if I'm making use of their services, I *should* be contributing to the site somehow. Yes, there are all the rationalizations of the Cult of Free; personally, I find most of them rather selfish and short-sighted. The morality entirely aside, if someone's providing a service I find valuable, it's in my best interest to help keep it running.
Fortunately, Ars (like many sites, and it's a trend I encourage) provides another approach: subscriptions. That is, you don't *have* to pay, but you can choose to instead. No ads, no information leakage through them (although Ars' own privacy policy *does* suck to a surprising degree), and a very quantified contribution to helping run the site. IMO it's rather pricey at $50/year, but if I'm being honest this is probably the single website I use most, so it's worth that much to me...