Having an open, accessible repository of scientific data sounds like a good thing, but I doubt it would help the problem of reproducibility.

The biggest problem of such a "github" would be that a scientific repository is only as good as its maintainer. In software development land we already see a lot of egos clashing over the code, but software has a clear "works/doesn't work" criteria. In many scientific areas such a criteria is hard to find and we'll have to rely on the personality of a repository maintainer.

The repositories will soon become a brand on its own. Think "nature.github.com", "physrev.github.com" and "lancet.github.com".