And for the sellers too. I've been using paypal for 13 years, and I've never had a single issue with anyone using a stolen card, and I don't think I've even had any chargebacks during that time. I previously used Worldpay and regularly had issues with chargebacks and fraudulent transactions.
Paypal goes to extreme lengths to ensure a transaction is not fraudulent. It can be somewhat annoying as they occasionally reject customers' cards for no apparent reason, but overall I appreciate their security measures.
Tip for anyone in Canada, Australia, EU or UK accepting US$ transactions through paypal: withdraw your money through Transferwise and you'll pay 0.5% instead of 1.5% or 2.5%.