Apple has past mastered using animation to aid both usability and fill transitions. An example of the latter is the "shrink" effect used when you hit the home button: whatever's currently on diminishes to nothingness and the home screen icons fly back into place. To do this effect, however, the iPhone takes a quick screen shot, and then uses the built in CoreGraphics/Animation layers to rapidly scale it down.
See the problem? No? Wired does: once a screenshot is taken, even if the iPhone immediately deletes it, those bits hang around inside your device. Current recommendations to properly destroy data involve multiple, pseudo-random overwrites. Absent that, forensics experts can often retrieve so-called "deleted" files. Including the screen shots the iPhone uses for animation. Including, potentially, any confidential or classified documents you were viewing -- or embarrassing Hello Kitty sites you were browsing --when you hit the home button.
Sure, this will likely never be a problem to most users. Passwords are obscured and not many of us have docs -- or look at sites -- that would be worth the significant forensic resources it would take to recover iPhone screenshot files.
But, a security/privacy concern is a security/privacy concern, and while this one doesn't trouble me personally, not knowing about it -- and making an informed decision based on knowing about it -- would.
And hey, at least it's not as tattly as Google Chrome...