As of 2013 Amazon have removed tagging from all Kindle books. I've no idea why they have done this. Perhaps they were being abused. Perhaps they were not useful. I have tried to find out from Amazon why this happened, but so far they have not replied.
It looks like the decision to remove tags has not filtered down to all departments in Amazon yet. For instance, the tagging feature is still available in the author page - you can add seven tags to your books, but they will now never be seen by customers.
It's a bit frustrating they did this without any announcements. I spent several fruitless hours trying to fix this. It's also frustrating that they didn't fix the author page so that you can still spend time pointlessly tagging your books.
In the long run perhaps this is a good thing. I spent a long time tagging because I read it was the right thing to do to help people find your books, but I never knew whether this actually helped or not. Now I don't have to bother to do this any more and I won't be at a disadvantage to people who spend time and effort tagging.
If anyone knows why they did this, please comment.
Update (17/2/13). Tags still seem to be available on the .co.uk site, but not on the .com site. No idea why that is either!
Edited transcript of my chat with customer service:
Me: Hi. I can't see or edit tags on any product
Amazon: I'm truly sorry, but the kindle books can not be tags. only some retail items can
if you wish I can transfer you chat to our specialized team for the more information.
Me:this is not correct, I have seen tags on books before but it has stopped working.
Also as an author I get to put 7 tags on my books.
Amazon:Yes you are right, before you can tag it, but now this function has been
removed from the kindle content.
Me: When did this happen?And is there anywhere I can read more about this?
Amazon:from the 2013, this function has been removed.
however I'll definitely forward you view as a feedback to our specialized and they will
definitely concern on it, Customer feedback like yours helps us continue to improve the
service we provide, and we're glad you took time to let us know. The Kindle Team will
carefully review your suggestions.