I just got scammed for 45 Euro and I had to look into ways to avoid this from happening again, I have called paypal and asked them to take legal actions against the person that managed to commit fraud not only against me, but many others besides... and they explained me how the system works.
As a seller, you must have seller protection at any transaction. Seller protection is valid for those who own a website from which the buyer is purchasing from, a website that offers invoices. Or you can send the invoices directly from your paypal account, without those invoices there is no seller protection. The payment can't be made by guest accounts since those DO NOT offer seller protection, therefor it is recommended to received payments only from your website, from what I understand guest accounts can't make such payments.
You can request at any time for paypal to take legal actions if you believe that the scammer commits fraud and/or they abuse the protection system, from what I understand this can only be done by phone and your case will be forwarded to their legal department, in the event that the owner's account got hacked, the legal actions will be taken against the person who accessed the account without permission, so I gather that someone will get punished after all.
Paypal representative told me that such things happen, that people take advantage and abuse their system, they said they were sorry and what not, but in the end I gather it is our responsibility to prevent such things from happening. They cannot update you on the legal actions they take against scammers, but the more complains they receive, the faster they take the legal actions against frauds.
If your transaction got no seller protection, you will not receive a refund of the money lost. In my case, I have asked the buyer to specify same terms and conditions as I would normally use in any of my invoices, but due to the fact that payment was done without the invoice, those terms and conditions became null/they were not taken into consideration and all they offered to do is refund 10 euro to me, as a seller.
I hope that information helps you for future transactions and to avoid getting scammed, I encourage you to always call paypal and explain your story and ask them to take legal actions against those who commit fraud, from what I gather offering any kind of services is NOT against the law, as long as it involves labor work or if you got full ownership of the items you're selling.