Assuming a merchant accept Bitcoin,

You as a shopper, place an order, and that merchant did not deliver, or sent to the wrong address, or sent a fake product.

You can not reverse the payment, you can get your bitcoins back, and the only thing you can do it leave a negative feedback.

Of course, there are many other scenarios, like phishing websites, fake websites, selective scams, and so on

What are your thoughts and ideas to prevent these scams.