You're correct. We know they have the ability, but they've never done it. They're not stupid. They know people are watching and that doing so will create a huge uproar. It would have to be something that's a serious threat to either Apple or their customers before they'd pull the trigger on it. Something they can hold up and say "We took extraordinary measures to protect our customers from this very serious threat," rather than something that would end up in the news like "Apple unilaterally removes purchased content from customer devices." The latter would be trigger at least a couple news cycles of Apple bashing, and fodder for competitors for months/years to come. Remember the uproar when Amazon did this with eBooks on the Kindle? They talked about that in the news for *weeks*.