Whitelisting apps will be more complicated, because they will need to block everything and only allow a subset, such as child-appropriate sites (by whatever standards they pick) or sites that never feature adult content or obscenity (again by their definitions). Apple says that too many over-broad matches are a problem, and the WebKit team’s blog post notes, “Using too many of them can cause the rule set to be rejected.” Because rules can be updated remotely and dynamically, this seems like a Safari limitation: It will opt to ignore rules if they wind up exceeding some thresholds at compilation time.
Some blockers will surely offer sync via iCloud or other services to allow any user-customized settings, like whitelisted sites, to be kept the same across multiple iOS devices—and perhaps OS X.
The differentiation isn’t going to come in performance, since Apple ultimately controls how that works in practice. Rather, it will be by features, usability, and cost.
A post-ad world?
This sort of behavior could be prevented with content blockers, because ad networks that employ such tactics quickly wind up on the darkest of blacklists, as privacy violators or script invaders, rather than just purveyors of commercial information.
A recent Reuters Institute for the Study of Journalism report found in a survey that 47 percent of regular online news readers in the U.S. and 39 percent in the UK regularly used ad-blocking software. Between this injection, the large amount of data loaded that’s not content related, slower load times, and privacy concerns, I expect content blockers in iOS will have the same level of popularity.
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