amok: he got banned because he 'gifted' many games to many 'friends' who in turn 'gifted' him back money. He openly acknowledge this is a post in the steam forums. We did this same thing in a thread a few months back, when you (I think it was you) tried to link several pieces of "evidence" where Steam supposedly banned people for no reason. Non of them held water...
ZPavelZ: I do not know whether it was me or not . And I repeat again. I have not seen any official notice from Steam. Until I see one the rest is only speculations. Sorry to be so blunt. That was initially my, rockpapershotgun's and everyone else's question. We all wanted an "offical, signed" statement from Valve. Why he got banned? Trading/gifting/selling? Ok, no problem, so be it. There was _none_. I said it so many times to so many people that I am sorry, if I repeat myself to you.
You will never see any official notice from Steam why any user is banned, because it will be in disclosure of personal information. The person in question do get noticed, they never get banned "without a reason" - they may not like the reason, or find the reason silly, wrong, short etc. but they will
always be given a reason. They can then try to rebut this, but the reason is there. However, this will be in a private conversation between the user and Steam, and it is then up to the user if they want to make this public or not. This user did so in the Steam forums, even copying parts of his correspondence with Steam there. However this is a long time ago now, and I really can not be bothered digging through the forums again.