I sold over 28 codes through eBay and they have suspended me for 7 days for listing. The safest way I can think of is to send it them with delivery confirmation and have a rule where you only accept payments from people with over 20+ feedback. I had two buyers once with about 4-5 feedback and they both tried to scam me.

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My collection and trade-list:
H: The Legend Of Zelda: Hyrule Historia LE in Mint condition W: equal value in trades or amazon/eBay prices
http://www.cheapassgamer.com/forums/...d.php?t=330790
My game plays:
http://www.youtube.com/tommylovehd