Re: When is ad-blocking ethical?
@N2 - "Sites exercise little control over who ultimately uses their advertising space . . ."
Pretty much this.
I do understand the way ad-slinging works and I do appreciate that it is not so straight-forward for sites to implement a more careful ad policy with greater control.
But that understanding does not change the fundamental problem, which is that the vast majority of websites that display ads simply rent a portion of their site for a third-party (often Google) to on-sell to, largely unlimited other slingers.
These ads are delivered via scripting languages and often contain scripting themselves. This is just plain dangerous and, whatever the 'ethics' surrounding ads and ad-blocking amounts to, the fact that allowing ads puts your computer at risk cannot be denied and should not be ignored or down-played.
Once that is accepted, the question becomes: is it reasonable to expect people to willingly open themselves up to (potentially crippling) data loss, identity theft, phising attacks and financial scams?
Or, put another way: is it ethical for a site owner to open visitors up to potentially malicious content that they either cannot or are not willing to control?
If a site only serves static, image-based ads (like a newspaper or magazine) then we have no problem and blocking them is, if not unethical, then at least a little bit selfish. But while the continue to serve ads that put visitors at risk, it is simply prudent for visitors to block that risk.
In other words, the way it is now, ad blockers are almost a part of your virus/malware protection, just as much as spam filters and AV programs, so asking users to disable ad blockers for a site is akin to asking them to turn off their anti-virus.