Pheace: It's not a flaw with gifting really. Gifting implies the thing is going to someone to give, not to trade. Verification is not necessary for that. They have a trade system for trading (within Steam).
hedwards: Yes, but it means that if you post a code, somebody has to redeem it in order to know what it is. So, unless they already own it, they have it whether they want it or not.
If your friends cause you that much concern then politely decline and tell them to send it to you via Email, that way you get to see what game it is before you activate it :)
Also, if you activate a key, don't you get a screen saying "you're about to activate game X" before you accept? I never had to say no but I figured it was possible?