He asked for 3 games from my "I have" list for something on his list. I didn't see anything there in my "I want" list, but I picked 3 games anyway on his list so he could get the games he wanted. Screenshot
(Here is the whole conversation for what followed: Steam Chat, but I will give a resume and write it here also for future proof)
On chat only minutes later he said that one of the games I chose was not more tradeable. I chose another even less interesting to me trying to help.
He sends the key for game in the last position in the list I had passed (less interesting for me). It worked.
I let him to choose which game I should send first. I sent to it. He said that was not possible to activate in his country. I told him that it was written in my description from which region I am and the necessity to check region before. He said that he didn't care to read because it was written in the bottom of the page after the "I want" list, I told him that it is the correct place to write the description on Steamtrades form and that I only followed the rules.
He also said that he LIED about his region, it is written on his Steam profile that he is from San Diego, California, United States BUT he is from ALGERIA (what a honest guy). And to my surprise he said it is my fault for the game not activating for him....
Anyway, trying to help (again) I sent another key, this time for the game on top of his list. It worked.
I was waiting to continue the trade for the other games. But he said that he did not want to continue anymore and was happy with this only trade. I explained that was not fair to pass the last game on the list I passed him for the game on top his list, and much more after I revealed the other key for the game that was not in his region and so he could pass it to someone else.
I asked only to continue the trade. At first he refused and left a positive feedback for me here on Steamtrades, but later accepted, only after choosing ANOTHER game instead. I again accepted his demands.
But this time he also wanted that I send the key first. I declined saying that it was he that kept changing (games and conditions) and lying (his region) and as he said, was very happy with the first exchange.
Of course, as every scammer, he said that even after all that, I have to send first now and it is MY fault that he lied, didn't read my description, asked for a trade and didn't kept his word...
In a last gesture of goodwill I tried to dialog. I learned the hard way that it is a vain attempt to dialog with SCAMMERS.