I'm mixed on this, as I don't think it's terrible that people should get to profit some from mods if they so choose, but there's definitely a lot of issues that need to be resolved. Hopefully Valve will work to improve this (much as they did for Greenlight, which had similar major issues and was improved).
Weirdly, I'm not the biggest Valve fan to begin with (and that extends to their games themselves), and I certainly don't like everything they've done with Steam, but overall I think they've done a pretty decent job of handling quite a few issues (although there's still plenty they could and I think need to improve), so I'm not really agreeing that this is just greedy money-grabbing on their part. There's quite a few people who seem to see every change to Steam as a step in the conspiracy for them to take total control over PC gaming, although there are issues with the amount of control they do have.
At this point, and I'm not saying people shouldn't be highly critical (in fact I think they should, just as I've felt people have every right to be critical in general, which has led to ridiculous attitudes in the console forum anytime a game gets criticized), but gaming in general you just have to know that its going to have issues upon release. Good companies work to fix the issues, and in my opinion Valve has done a reasonably acceptable job of doing that, and I'm hoping they continue to do so.
Definitely the revenue share needs to be adjusted, 25% is way too low. I could maybe see it if companies were doing a lot to help the modding community, which I don't think Bethesda has (they've pretty much just made it reasonably easy to mod, which sadly is a big improvement over most games now where companies are more actively trying to limit if not outright ban mods).
I'm also a little baffled why people are surprised over Skyrim being the start of this. It's a very popular and fairly cheap game that is both known nearly as much for the mods as the game itself, and the mods have kept it (and other Elder Scrolls games) interesting far past their release dates. Seems like the perfect game to try this.
I think Valve just didn't think this through properly. My guess is Bethesda contacted them about it and Valve figured they had most of what is needed to make it happen in place, and figured it would actually be positive for people as modders get paid, and it would give people extra incentive to mod (and try to improve mods) which would then benefit people playing the games. But they didn't do due diligence on all the issues. We'll see how it turns out and if they're willing or even can mitigate some of the bigger ones enough to make this positive.
OMG the last paragraph in that reddit post...
Real-time update - I was just contacted by Valve's lawyer. He stated that they will not remove the content unless "legally compelled to do so", and that they will make the file visible only to currently paid users. I am beside myself with anger right now as they try to tell me what I can do with my own content. The copyright situation with Art of the Catch is shades of grey, but in Arissa 2.0's case, it's black and white; that's 100% mine and Griefmyst's work, and I should be able to dictate its distribution if I so choose. Unbelievable.
I can't wait for someone to sue over this. One has to wonder if this really wasn't some half baked scheme to just destroy the modding community.
While that sounds bad, you have to understand Valve likely is just aping the policies of most sites that host content created by other people and that their policies are actually there to try to keep content from being taken down for frivolous reasons (although if it's a large business able to threaten lawsuits then they have more power to get content taken down). But it does present major problems as a lot of people make content and then people steal it and post elsewhere. But maybe it is different as generally other sites do take things down without official legal representation when provided with enough proof.
I think the issue here is the weird area in that people paid money for that content so from Valve's point of view they're trying to protect them (wasn't there a big fuss about a company pulling their game and it getting removed from people's accounts, that could have setup a policy about similar that's being applied here), hence them requiring legal compulsion.