Paypal has never banned any PTC. The problem is created by the PTC owners itself. They sell refs and upgrades, that's an investment and as per Paypal policy investments are not allowed and you see the sites which donot sell refs are still paying by Paypal.
The other problem with Paypal is created by scam site owners as icashout. Members asked for refunds and chargebacks. Again as per Paypal policy they can ban account if they receive disproportionate amount of chargebacks, complaints etc.
So now we have to use Alertpay as the next Paypal for these sites. But Paypal is till date the best, reliable and secure online payment processor.