I tried selling these on HackForums about an hour ago since I thought they would go faster there. I got scammed out of two codes already by "trusted" member.
Only taking BTC. Will go first to trusted members. I have 8 of them left (after getting scammed twice). They were all attained legitimately. They're worth $100 USD when you add them to your Steam wallet.
You can see I've redeemed a bunch, there's been no issues with my account. That account ended up getting banned and I lost $300 in guns and a MW doppler tho @_@. But there is no risk to your account, nothing like that.