I think archives with pretty low standards for notability are a good idea. At some point though you have to pick what actually counts as interesting enough to go in the curated list that is actually suggested reading, where the prestige is attached. If there's no curation by Nature then it falls to bloggers or another journal to sift through the fire-hose and make best-of lists. Most of the value is in the curation, not the publishing. Without exclusivity there's very little signal.

> The marginal cost for publishing a study online at this point is essentially nil.

The marginal cost for doing a study remains the same, which is quite a bit. Society doesn't have unlimited scientific talent or hours. Every year someone spends replicating is a year lost to creating something new and valuable.