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.
Well to dodge this kind of scams is very hard because this kind of things happens to any us users. But to solve this kind of stuff is just to be wise on what you will decide and search about the information about the website that you will shop, and don't trust people in the internet easily because they can be that wise to scam you

.. get the info about the website and you won't be scam,