In iOS 9, Apple introduced the ability for developers to create content blocking extensions for Safari, which have a large number of theoretical uses. However, the primary use for this type of extension seems to be to create blockers for ads and tracking scripts.
In case you haven't heard, there has been a bit of controversy over these types of applications. Most notably, well-known iOS developer Marco Arment (of Overcast, formerly Instapaper), created a content blocker named Peace, which he pulled from the App Store shortly after release, citing a guilty conscience as the reason.
If you read any of Marco's posts during the launch and withdraw of Peace, you could tell that Marco was clearly conflicted. Ad blockers are a tricky moral situation.
When it comes to most factors, the web is in the best shape that it has ever been in. However, when it comes to advertising, the web is not healthy.
I fully support the use of advertising as a way of subsidizing free content. Ad-supported content allows anyone access to most of the world's knowledge, preserving the open nature of the web. However, advertising in its current form is a cancer that is slowly destroying the web.
Most publishers have little control over the ads that their networks display on their sites, so reputable publications are stuck with these toxic ads. And many sites rely upon ads to support their operations, so they have little choice but to accept the malicious practices of the major ad networks and advertisers.
Like I said, advertising on the web right now is like a cancer. If left untreated, it will kill the web. If we don't fix the advertising problem, more and more content will get locked behind a paywall, disrupting the open and democratic nature of the web. If the advertising problem is not fixed, only the wealthy elites will be able to access the full web, while most people will be living on a crippled, limited version.
But treating the advertising cancer will have consequences. Ad blockers are like chemotherapy, generally effective in their goal, but with great consequences. As we attack the advertising issue, there will be casualties. Sites will need to adapt to new models of making money. Some won't in time, and others simply won't be able to.
The war on ads is coming. Not all sites are going to make it out alive. But this is a pivotal moment in the history of the web.
2016 is going to be a rocky year.