Except they created a market place without restriction to sell / trade those items. So yes Valve is to blame. The whole thing with auction house on third party

Except they created a market place without restriction to sell / trade those items. So yes Valve is to blame. The whole thing with auction house on third party sites is Valve fault, not sure how you can defend them. Also it's not only cosmetic since you can have weapons / items in those crates.