I searched the comments here and noted that no-one has mentioned that Ars are owned by Condé Nast, a company with an estimated $4-5Billion+ annual revenue. They also own Wired and Reddit, let alone Vogue, GQ and numerous other publications.
Why do I mention this? Context. If Ars was still an independent operator then I'd have more sympathy for their argument, and yes they still have numbers to maintain... but have you considered their sister magazines, take Vogue/GQ for example and think of page content vs pages of advertising. I watched "The September Issue" a few weeks ago and the thing that stuck in my mind was that that issue of Vogue had about 800 pages and only over a 100 pages were actual content, the rest were adverts. Fucking nuts! So yes, the argument of advertising driven content isn't going away and we'll see what happens should Mr Murdoch (who seems to want to own every content producer on the planet) try his pay-wall experiment.
As for ad-blocking... I continue using it and am glad since I've seen the latest shit that people have to deal with, auto-loading videos, sound, fly-outs you can't shut, flash ads that grind your page to a halt, as well as the malware that floats around and even hits high profile sites... I want control of what opens up in my browser and the only ads I'd ever consider are Google textual ads... why? cos they don't piss me off. Advertising should be an enticement of a good deal, done in a thoughtful and pleasant manner.. Unfortunately the Advertising 'industry' (I also include SEO bastards too here) battles everyone to promise customers the Earth while pissing off the very people they're meant to attract, they go through periods of continual fads in order to push shit and pretend to everyone they are 'unique' in their services, yet do the same as everyone else. The arguments from most advertisers that people who use ad-blocking software need burning at the stake tells me a lot, in that they just don't 'get-it', a good advertiser/marketer will have spent time arguing both camps and understand the issues at hand (as well as the people they're meant to be advertising to) whereas the rest fail at being the clever people they advertise themselves to be.
My suggestion to Ars, if it is that much of an issue then block your content from being shown 'full-stop' to anyone using ad-blocking software as you did in your experiment... then you only have to serve a minimal bandwidth using text page explaining why, fucking deal with it instead of whining like everyone else (i.e. News Corp, et al). The advertising industry won't die, but it will contract, change and evolve. But as a web browser I will not be dictated to that I have to have certain content forced down my throat, and I will control what I choose to see. There are multiple revenue streams possible, and I view Ars as producing higher quality content than a lot of other sites out there that I would be willing to pay for if I visited it enough (El Reg, BBC News, Slashdot and Fark tend to be my usual reads, and as a TV license holder I already pay for BBC News). Going back to context again, it would also be handy if Ars was to tell us their average percentage of userbase are that employ ad-blocking, which as a tech site I'd guess would be higher than a regular new site.
Sounds like you got the skinny on the whole situation.
I took a fish head to the movies and I didn't have to pay. -- Fish Heads, Saturday Night Live, 1977.