On could argue that this is scanning is also opt in, it requires you to purchase an iPhone. Also, at least according to Apple's provided material, the scanning

On could argue that this is scanning is also opt in, it requires you to purchase an iPhone. Also, at least according to Apple's provided material, the scanning only affects images which are uploaded to the iCloud, so not every image on the device. However, how long that restriction actually holds once the system is in place is questionable. Also, the risk of abuse by authorities as well the fact that there is no way to monitor the system as a user is a huge part of the problem.