So unless the developer/publisher sign off on the mod it shouldn't be distributed? Even if it's free? What if it's for a game published by 505 or any number of other publisher/developers that don't even put the vanilla game through QA? What if the mod is made to fix a broke game (kind of like the unofficial patches games like Fallout 3 receive) but due to dev/pub ego they don't get the stamp of approval?
I'm not sure I think that's a good idea.
As for charging for mods; there's two sides to this coin. It could be very good or very bad. It was; however, inevitable. It's still not necessary for a fee to be charged and is totally up to the modder's discretion, but I don't see an issue with giving modders the avenue to make a profit from their hard work.
Vote with your wallet. If you don't think a mod is good enough to buy then don't buy it.