@splodge: Apparently this has been going on, with folks downloading mods from the Nexus and putting them on Steam. Don't see any direct way on a mod's page to report it.
Why would I ever make a mod and try to sell it when any chump could just re-package it and sell it for less. At least the mobile phone app stores have some procedures in place to eventually get fraudulent apps taken down. Judging by the way Steam are handling this, it will be entirely up to the person affected to get it taken down. Just ask nicely, I guess? Please sir, could you please take down my work?
I like the idea of mod makers being able to make money, but without giving them protection and adequate tools to make sure their work is not stolen or duplicated on a platform that has none of the anonymity of torrent websites, I can't see this ever being a positive thing. Why give scammers and thieves an avenue not just to copy others work, but make potentially large amounts of money?