Is Smartcanucks like a polite version of RFD? Or are they also vultures?
AFAIK, Paypal should have some sort of seller protection policy against buyers who lie and claim they never received their item (or if said item really was lost in mail).
When you sell something on ebay, there's a link that lets you exclude places you don't want to sell to, as well as certain types of buyers. While it does limit the number of people that can buy from you, well you don't want to sell to them anyway so w/e.
Or you can just do what I do and refuse to ship anything anywhere on ebay without tracking and insurance. ebay is a buyers paradise and a sellers nightmare, the only way to get around all of the scammers is to stand your ground on only shipping via a tracked method.