For many people the iOS 7 parallax effect is cool, dynamic
wallpapers amazing, the Messages bubbles fun, the folder and app
zooming transportive, and so on and so on. For those for whom they
trigger motion sickness, they’re off-putting, nauseating, or
simply impossible to use.
Parallax can be turned off in Settings > General > Accessibility >
Reduce Motion. So can Dynamic wallpapers in Settings > Wallpapers
& Brightness. Message bubble bouncing, folder and app zooming, not
so much. Apple also provides UI Dynamics as an application
programming interface (API) so developers can more easily add some
of those effects to their own apps. Those often can’t be turned off
either. That some of the effects can be turned off means Apple
probably foresaw at least part of the issue. That all can’t means
they probably didn’t foresee enough of it.
Interesting side-effect of the new z-axis spatial interaction in iOS 7.