Trader olafkswg recently drew attention to the blocking of a large account on Steam. Valve has banned a user who had assets totaling over a million dollars (80+ million rubles).
His collection included various skins, cases, as well as particularly valuable «Katowice 2014» stickers.
Another screenshot shows a notification from Steam (in Chinese) mentioning fraudulent activity in the text:
«..."Fraudulent activity is defined as a violation of the Steam Terms of Service, or participation in criminal activity, including the use (or attempted use) of stolen credit cards, distribution of stolen items or games under seal, use of other accounts, and profiting from captured or stolen accounts."»