Previewed at WWDC, launching in the fall.
Copy and Paste Implementation, Exchange Support for iPhone?
The validity of the comments are in question as it seems unlikely that an Apple employee with this knowledge would necessarily speak freely about it at Macworld. The claim is that iPhone Copy and Paste is being actively developed, but how exactly to implement the functionality appears to be up for debate.
The trouble it is having is implementation. How to easily call up a copy or cut option and then the paste action. Its probable that the zoom bubble (the one that brings up the edit cursor) is the issue as it has removed the obvious tap and hold position from Apple to use for a pop-up menu of some sort. Text selection is another difficulty to sort out. Certainly, the cursor could be added to the menu selection; however, Apple wants to keep this as simple as possible and that added step would not lend itself to simple.
Historically, Apple had already addressed a menu-less copy/paste in their previous touch-based handheld, the Newton. A description and video shows how Apple implemented Copy/Paste on the Newton, though it would conflict with the press-hold magnifying glass in the iPhone.
Other iPhone users have suggested alternate possibilities (screenshot, mockup video) but these also suffer from complexity issues.
Meanwhile, the Apple representative also claimed that "Apple's aware of the Exchange need" but stopped short of confirming that it was coming.