This is the definitive question that has to be asked of anybody proposing a repeal of 230. I personally dislike 230, and have from the beginning, but anybody who doesn't have a direct and complete answer to this question isn't being serious.
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I personally think that the answer is to standardize terms-of-service documents and to make them into real legal statements that both the website visitor and owner can make claims regarding, and that those statements be registered with a federal agency. The standardization should be so tight that filing it should be a matter of picking from drop down menus on a form, and the implications of each choice should be common knowledge and taught in school. The form should be able to be filled out anonymously (as "owner of [X] site.")
If you run a site without having filed one, though, you would lose legal protections as a publisher based on modding behavior. If somebody filing suit can point out any decisions that have been defined by law as constituting a specific degree of editorial control (examples: spam-control, abuse-control, subject-control, position-on-a-subject-control, arbitrary-control, etc.) then they will be responsible for libel/tort claims as a site for individual posts. A site that has filed a terms-of-service will get the benefit of the doubt, and the ability to push liability onto completely onto posters or maybe even individual mods.
Those requirements would either be too onerous to run the walled gardens of Web 2.0 at scale and small players will have a profitable business opening again, or the big dogs would be forced to really bureaucratize or democratize, and small players will have a profitable business opening by providing them modding services at the forum level.