This is very, very important. A disclaimer, whether it is in a review or it is the one that I am an Amazon Affiliate, can be the difference between having your account and losing it.
That said, I am an Amazon Affiliate. If you purchase something that I have linked, I do get a commission for selling it to you. Simple as that- my site is monetized and I’m not going to hide it. It’s in the widget menu on every page.
And you shouldn’t hide your review disclaimer when you product test either.
You don’t have to be blunt, “I got this for free.” And you won’t always get the items for free. But you HAVE to let them know that you got it at a free or reduce price if you are a reviewer.
That means, “I received this item for quality testing purposes” or “I received this at a discount for my honest opinion” are much better than “I got this for free.” It keeps people from harassing the seller for free products, and makes people a little less likely to down vote your reviews because you got something for free that they are paying for.
And it also means that Amazon won’t look at your account and go, “Hey, (s)he isn’t following directions. Account deleted!”
Prime gone, all your reviews gone, everything you’ll have worked so hard to do by building up your reputation, gone in an instant. Because you couldn’t be bothered to add 8 words to your review. You may even wind up IP banned- and anyone who shares that IP could be screwed to.
So make sure you add your disclaimer. It’s important. It can go at the beginning, the end, the middle- it just HAS to be there. Work it in naturally, if you can, but don’t forget it or make it so obscured they can’t tell you used it.
Just an FYI. Don’t play fast and loose with them, you won’t win if Amazon decides to play hard ball about it.