Yep, all the reviews I've ever posted to Amazon have disappeared. I'm not sure why - I noticed last week, and my initial feeling was that it must have been an IT error.
However, Gathering has just lost a review as well, so I wonder if Amazon has a new algorithm for cracking down on "fake" reviews - and it's throwing out the baby with the bathwater?
I don't see how I could possibly have broken Amazon's rules, though perhaps being the first reviewer on a few books might have raised a flag. Either way, I've emailed Amazon support about this and hope to get this resolved.
It does mean, though, that if you're an author here and I reviewed one or more of your books, those will now be missing on Amazon - though my Goodreads reviews don't appear affected (look how fake they are - lol!).
I do have a couple of reviews outstanding - Ellis Knox's Goblins at the Gates, and Ray Bradbury's Farenheit 451 - but I'll wait to see what happens before posting anything to Amazon or Goodreads.
UPDATE: And... they were re-instated! See this post and the one following it for more information/speculation: All my Amazon reviews have disappeared!
UPDATE 2: I now suspect the reason my account was flagged was due to a high ratio of self-published books (especially ones with relatively few - if any - reviews) being posted.