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.
There will always be people who stumbles upon a fraud. However as with all payments made to persons, do your reasearch.
Also, I'm sure there will come more and more companys who buys for you that meaning a 3rd party who makes your purchase (you pay a small fee for them doing so) but your initial payment is safed so if it's a scam it's the 3rd party that will lose on it, not you, well as long as the 3rd party is trusted of course.

Best Regards,