We've mentioned their easy to use returns form before, which lists your order items so you can mark which ones you're returning. What's interesting is that you enter a number next to the items stating why you are returning it, the reasons include:

• The item wasn't as it appeared on the website
• Customer ordered more than one size
• Order didn't arrive in time
• Item was faulty
• Incorrect item received
• Item doesn't fit

I can think of several reasons to do this:

• This feedback can be used to reduce the overall return rate, for example if many customers return a specific item because they claim it isn't as it appeared on the website, the photography and item description should be reviewed.
• Analysis of the overall reasons may be useful for understanding customer behaviour.
• If a specific item is being regularly returned because the customer complains it's faulty, this can be investigated further.

In short, information on why an item is returned can help optimise your fulfillment process, spot problem items (either the item itself or the webpage describing it), all whilst improving the experience for future customers.