Aristotle once said "that which is common to the greatest number has the least care bestowed upon it." This idea has subsequently evolved into the modern concept of Tragedy of the Commons (or not quite modern - the term in fact dates back to an 1833 study of medieval land holdings). The concept itself is quite simple: free access and unrestricted demand for a finite resource ultimately structurally dooms the resource through over-exploitation. Oddly enough, the concept applies itself just as well to shepherds bringing their flocks to graze in the village commons than it does to Internet ad-blocking technologies.
Here the chorus of user-rights advocates will usually respond by saying that such a comparison does not properly apply: the Internet changes everything, digital resources are not finite. However, online rights supporters often forget that while content on the Internet is infinitely copyable, the generation of that content (especially of high quality, useful content) is very much finite. If one user "maximizes" her consumption of Internet content by blocking ads, little harm is done to other users or to the content generators. Yet if all users were to follow this behavior, the content generators would no longer have reason to publish on the Internet, and these users then all suffer from a lack of content. It's the same situation as when every shepherd maximizes his flock in the village commons, resulting in a lack of sufficient grazing land for any given flock.
There is no doubt that ads are now big business on the Internet. Google posted 2006 revenues of over $10 billion almost exclusively from ads. Last year, American television stations charged YouTube with copyright infringement for showing free clips of their shows, only to then show the same clips for free on their own websites (with their own ads). The New York Times recently eliminated the subscription requirement to read op-eds from their website, calculating that more revenue was generated from ads on the site than from subscription fees. While there's obviously a business interest in banning ad-blocking technologies, could such a law be passed?
The obvious parallel here is to the anti-circumvention measures in the Digital Millennium Copyright Act. Just as it is illegal to create or possess a program that circumvents copyright protection in media and software, one could easily imagine a similar restriction on ad-circumvention technologies. The problem is that copyright infringement is a well-recognized offense; there even exists criminal penalties for the more egregious cases. Conversely, there exists neither civil nor criminal sanctions for "not viewing a commercial". The American Betamax case serves as an appropriate reminder of this proposition. Furthermore, Justice Posner's derivative works argument, rejected in the Betamax case, is even less applicable to Internet banner ads: arguing that a randomly-selected 1"x6" banner-ad forms an integral part of the "work" that is an Internet website seems to me a tenuous proposition at best. Of course there is always the contractual option for content generators: restricting access to your website until users click "I Agree" on a clickwrap agreement that prohibits ad-blocking technologies. We know from Rudder v. Microsoft that such agreements are legally enforceable in Canada, but the question remains of how to enforce them.
As the music and movie industries can attest to, enforcing any laws or agreements against technologies available on the Internet is next-to-impossible. In this case, there are three parties against whom action could be taken: the developers of such programs, the users and the ISPs. We know from the Tariff 22 decision that Canadian ISPs are not de facto liable or responsible for the conduct of subscribers on their pipes. The developers of ad-blocking technologies most likely do not reside in Canada or the US and, in the case of open source-developed programs, these developers are both anonymous and number in the thousands. Finally, attempts at suing users of ad-blocking software will run into the same problem encountered by the file-sharing opponents: what damage does an individual cause by not viewing one, or even a thousand, banner ads?
The battle over ad-blocking technologies is not one that will be fought in courts or in legislature but rather online, pitting technology against technology. If content providers truly want to protect their revenue stream, they should design website in such a way as to block ad-blocking programs. Any pleas to users to stop using such programs will be met with one of the file-sharing movement's favorite slogans: "Your failed business model is not my problem".