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 are less cases where a seller scams as compared to the buyer's scams and hence if chargebacks are allowed almost all the sellers would be worried. This is actually the biggest drawback with paypal and a reason why mos of the people prefer bitcoins over paypal.
And how can a seller scam man ? I mean you would of course buy from genuine and verified users, no ?