The ambiguity of the supposed incident we are discussing doesn't help clarify things, so let's apply the Steam case to the mall metaphor. What exactly was the offense? A customer bought a product offered by a mall store from a retailer outside of the mall. How does that qualify for a total ban from the facility?
I'm pretty sure there is more to it than just that. There would be no way for them to track a gift code going over ebay if it was purely legit (I.E. something like me buying the OB and selling the extra HL2 code that comes with it for a few bucks) There's no possible way for them to track that somebody payed me money for it before sending it.
My personal guess is that someone fraudulently had gotten a ton of codes to sell and valve just wiped them all out.
I do fully agree that it should not warrant a ban, there is no reason why they cant just take the game away. Though now how would you guys feel if they had the ability to physically delete a game off of your hard drive in such a case? They cant just remove it from your steam account if you have it installed already. I'm pretty sure that would not go down well with most of you, so what would be an alternative?
And I've gotta say, I personally have gotten a steam account disabled, I was young it was when steam first came out, My mom would not let me buy HL2 the day that it came out, I had to do my massive amounts of homework first which ended up taking me all weekend. So I stumbled upon this claimed method to get HL2 for free, you put in 000... as the credit card number and cancel at a certain place. Long story short my account got disabled for credit card fraud. I had learned my lesson.
I also think there should be a warning system, 3 strikes or something like that. I can see why they do not want you on their service for say doing a charge back after buying a game. But I do agree that losing all of your games retroactively is basically abuse.