They don't have to sell the content. Writers can seek vendors and produce "sponsored content". This is likely to skew and fuck up free literature as we know it, but it's done routinely, and for free: people write tutorials for vendor's services and products with no commission (how much effort has gone into "teaching" Google Adsense by SEO professionals who only wanted to pad their resume? would be nice if google sponsored the texts, but they wont, so it's time for authors to look into less known vendors and introduce their products to the reading masses for a fee.)
Or get a better advertising company: [Shameless, but very muted plug] :-)
[Edit: this is strictly for the non-fiction trade publications, the sort of stuff that you typically see on Scribd. Fiction might have a better future in ebook readers and their associated online shops]
For fiction, http://StoryMash.com is doing exactly this. Writers earn over 50% for their collaborative content. Today it all comes from advertising, but when the first great internet novel is re-published, the participating authors will see a real payoff.
Or get a better advertising company: [Shameless, but very muted plug] :-)
[Edit: this is strictly for the non-fiction trade publications, the sort of stuff that you typically see on Scribd. Fiction might have a better future in ebook readers and their associated online shops]