I choose not to insure my iPhone, but the cost of the handset is not necessarily the main risk.
My last phone (which wasn't an iPhone) was stolen, and the thief made £180 of calls in the relatively short amount of time before I discovered it had gone. So not only did I have to buy another phone, but I had to pay the bill as well. The bill could have been a lot higher. Some of the better insurances cover you for the cost of calls as well as for a replacement handset. It's worth checking the details so you know exactly what you're getting for your money. You then have to compare the cost with the risk and make your own choice!
I'm a lot more careful with my phone now, and always have a PIN number on it which could at least slow a thief down a bit and prevent an even bigger bill before I realise it's gone!
Edited by rushmere (Tue 27-Jan-09 22:01:27)