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.
That's the main reason bitcoin will never be massively adopted for online shopping, unless transaction escrow and transaction disputes are managed by some Paypal alike corporation and bring some security to buyers.
You can see it happening all the time on dark markets, not only high reputable sellers make an exit scam, entire markets exit scam.