Without getting into the weeds of arbitration—if you want to sue Valve for some reason, you now have to file in King county, Washington. This makes it too expensive to be worth it for any amount less than the cost of flying to and staying in Seattle for a lawsuit. Even if you’re right and Valve is wrong.
Amazon recently did this too and it worked out well for them I guess, since other companies seem to have followed suit.
This is not even remotely new.