I run a small exchange and I can tell you my statistics, out of 50 orders 49 would be a scam.
Famous PayPal chargeback will chop off the balance from your bank account or credit card, will bring you overdraft fee and charge-back fee on top.
I don't think the fraud rate would be quite this high but I would agree that it would certainly be very high. Probably higher then being in this business would warrant.
The sites in the OP (and any other site that accepts PP for BTC) all charge rates that is well above the going market rate for bitcoin. This makes it a very uneconomical way to purchase bitcoin as it would be much cheaper to chashout of PP to your bank account and then purchase bitcoin via an exchange or LBC.
You spoke well but not withstanding what do you think of countries who got no option of withdrawing to the bank they can only send via their cc through paypal?