I see nothing whatsoever in the situation that involves free-ridership; advertisers buy opportunities to advertise that they think promising, not rights to have the advertisements seen. It's no more free-ridership to block pop-ups than to ignore a billboard in a stadium, skip over advertisements in magazines and newspapers, or leave the room during a TV commercial, despite the fact that these all tend to make things cheaper. Junk mail makes the Post Office money and thus more sustainable; I think the Post Office is a dandy thing, deserving both of money and being sustained; but I will deny to the end that any bulk mailer earns thereby the right for me actually to read all the junk mail advertisements I get.
I do think that the fact that anyone could suggest there's any sort of a free-ridership in the matter is a sign of how nearly insane our acceptance of advertising has become. If someone is not paying attention to an advertisement, whatever the means by which they avoid paying attention, that's just ordinary hazard of advertising. They are still getting exactly what they are paying for -- which is that their advertisements be out there just in case someone does pay attention. That's the only thing they could possibly be paying for.
Contrast the standard pop-up ad case with a different kind of case: an advertiser approaches me in particular and offers to pay for a set of subscriptions in exchange for their sending me ads at various random intervals whenever I'm in the subscription zone. It seems that the case that I am free-riding would be much stronger here than in the standard pop-up ad case. But, unless it is in the contract I have agreed to that I will not block the ads, it still doesn't seem that I'm free-riding if I block the ads. The advertiser is paying to send me ads: nothing about this obligates me to do anything in particular with them, any more than I am obligated to read the emails sent if, to get a free prize, I sign up for a mailing list. Advertisers in such cases are not buying or trading for rights to my attention, but for permission to make use of a particular channel of access to me, one that I am still free to use or ignore as I please. But in cases like snail-mail junk mail or advertising on the web, there is even less grounds for any sort of moral debt: if people don't automatically get the rights to my attention by the fact that I myself have given them permission to send me things, they certainly don't automatically get it if someone else has given them permission. Advertisers don't buy the right to get my attention; they merely buy the right to try. And that's pretty much universal.
The basic argument in the article is this:
The Web is governed by an unwritten contract: You get nearly everything for free in exchange for the hassle of a few ads hovering on the periphery—and occasionally across the whole screen for a few seconds. Advertising probably supports a huge swath of the sites you regularly visit. It's obvious how rampant ad blocking hurts the Web: If every passenger siphons off a bit of fuel from the tank before the plane takes off, it's going to crash.
There is, however, no such unwritten contract. The Web is in fact governed by written contracts; namely, the written contracts by which advertisers pay for advertising space. Yes, I am getting many things free, and other things at least cheaper, because advertisers are doing this; yes, if web advertising never worked, there would need to be other means of supporting this rather expensive luxury. But none of these add up to a free-ridership problem. As I noted in my comment, advertisers are getting exactly what they pay for whether I let myself see their ads or not; the only thing that changes if nobody sees the ads is that it turns out the advertisers are wasting their money by supplying that venue, at least to the extent that they are trying to advertise, rather than trying to do a service. (It varies considerably, but I'm not a pure cynic about businesses that advertise; I think in many cases they really are trying to do both -- i.e., do good for people and get good advertising out of it at the same time. The latter simply makes the former a sustainable activity for them.)
Ah, you might say, but isn't this precisely what a free-rider problem is? I am paying less than my fair share, or at least, I am getting something free at the expense of someone else. But this is not sufficient for free-ridership. Genuine free-ridership requires (1) that there be something I am receiving with very little trouble at the expense of someone else; (2) that this must be a good resulting from our collective action; and (3) that there is some reasonable expectation that my part in the collective action is to do something that I am not in fact doing. (It's nonsense, for instance, to claim that if a toddler benefits from collective action that the toddler is a free-rider. The toddler is simply not a part of the relevant decision matrix. Likewise, if I invite you to my tupperware party without making clear beforehand that you need to attend a presentation at the end, and you don't buy anything or even pay attention despite eating a lot of my food, you are not free-riding; you are a free guest whom I am hoping to interest in a business transaction, and that's it: it may not be turning out the way I hope, but I've gotten what I've paid for, and you don't have any obligations to do anything in exchange for the benefit of the food as long as I don't throw you out. You can fall asleep during my presentation, play on your iPhone, whatever. My bad luck in inviting you, or my mistake in the kind of invitation I gave.) Merely benefiting from someone else's action is not free-riding, even if I never return the favor. But, again, in this case, I am doing all anyone reasonably expects anyone to do in response to advertisements: that is, pay attention to them if I want and ignore them if I don't. If the website takes money from the advertiser and then sabotages its ads, that is free-riding. To be sure, since the advertiser is looking for an effect, it's all the same to them whatever the reason for their advertisements not actually reaching me. But again, whether it's an ideal situation for the advertiser or not, the advertiser is not paying for an ideal situation: the advertiser, in the hope of reaching people, is simply paying to use a channel of access, and if the website fulfills its obligations they are getting that even if they never do reach people. To put it in other words, I cannot be a free-rider, because, although I am a beneficiary of the action, my actual attention is not part of the relevant decision matrix, only the chance to try to get my attention by a particular means -- and even that does not directly involve me. It's a decision matrix constituted by the preferences of the website and the preferences of the advertiser, given the probability or improbability of my paying attention to the ads; I'm not actually part of it at all, but more like a guest that a website has freely invited in; advertisers support and sponsor this invitation in the hope that it will lead to a business transaction. And that's my entire role: to be there if I want to be.
Indeed, one could argue that advertisers are themselves the ones who have to be careful to avoid free-riding. If they could guarantee getting through to the public, they would then be receiving the public's attention without the public's permission; they would then be reducing the amount of attention available for other things, many of which are good and many of which are certainly better than the advertisements themselves; and they are getting this good of the public's attention without properly reimbursing the public for the intrusion. Advertisers are, in short, in constant danger of being free-riders on the public's good will, when it comes to what they tolerate as taxing their attention. I suspect that it's only in fairly extreme situations that this definitely occurs; but if any advertiser were to complain about my blocking their advertisements, I would simply complain right back about the fact that, without any explicit permission from me, they are pretending that they are entitled to waste my time. And I would be at least as right as they are.