Hi Sporadic, I think you have to buy 'anything' from Amazon to be allowed to write a review.
I logged in to my Amazon account and I tried to write a book review. I receive this message:
"
Want to write a customer review?
To write a customer review: you must have used this account to complete a purchase* of an item from Amazon.com. Please wait 24 hours after your first purchase before writing a review.
If you have another account: and you have already used it to make a purchase, you can sign into that account to write a review."
* A purchase requirement is used to maintain review quality
See
http://www.amazon.com/review/guideli...uidelines.html
"
Who can create customer reviews?
Customers! Anyone who has purchased items from Amazon and is in good standing in the Amazon community can create reviews."