When Apple didn't implement copy-pasting on the iPhone since version 1, I had just assumed it was a UI issue (Eg. they were waiting until they figured out a good UI for it). Now however the idea is out there and Microsoft still released Windows Phone 7 without copy-paste functionality, promising it will be ready in a few months.
My question is: Why does this takes a few months to implement? Are there some technological challenges that are unique to programming for a touch screen that I'm not familiar with? For that matter, what are the unique challenges in doing X in a touch screen app?