I was originally enthusiastic, or at least admiring, of the news that Prince Harry will be deployed to Iraq. But Ankush makes a good point here:
He's going to be a prime target for insurgents and militias, which means the British army is going to have to divert resources to provide extra security for him and the people he's working with. It's going to be a distraction, and, in the event he's ever captured by a militant group in Iraq (heaven forbid, etc.), it will be a monumental disaster for the British army, the British government, and, indeed, the British people.
That all seems right. Now, I'd assume that Harry will go and be sequestered in a base somewhere, but what I'd assume and what might happen are very different.