I would say the risk is for the consumer, since there are quite a few ways your credit card info can be stolen online when you are buying. Since Jeff covered the seller part of security pretty well, I'll talk about some ways you, as a buyer, can shop more securely.
Site Security: Make sure the website you're buying from is secure. Check out what security features they have and how long they've been operating. Do they have legitimate contact information? Google the site's name before you buy from them. This is crucial to determining whether an online store is a scam or not.
Connection Security: Make sure you're on a secure internet connection. Don't buy things or enter your credit card info when you are logged onto public Wi-Fi. These are not encrypted and easy to hack.
Computer Security: Make sure your computer is free of viruses, trojans, and keyloggers. Some of these can easily capture the data when you type in your credit card information.
Excluding that, some credit card companies will give you temporary, one-use, credit card number for shopping online. Hope that helps!