I've sold a lot of graphics card on Ebay over the years and have actually never had a problem (though I did have a scammer buy a RAM kit from me once). I think the one I was most worried about at the time was when the buyer for an R9 290X turned out to be in Mexico, but I shipped it over and everything went just fine. That was around the time of the first mining boom, so I guess it probably ended up in a mining farm.