Nature Communications is to become a fully open access journal. Until this time Nature Publishing Group has only published hybrid journals under the Nature branding. To recap: hybrid journals offer a choice between traditional paywall publishing (where the research output is viewable via subscription), or "gold" open access where the author or institution pay an up front fee for publication. The decision to make this "flagship" journal fully open access was taken in order to drive the group's commitment to Open Access.
"[W]e believe in Open Access."(Nature Publishing Group)
In the press release Nature Publishing Group included a statement from Robert Kiley of the Wellcome trust. Kiley is quoted to say that the move by NPG provided evidence that hybrid publishing can be a "transitional phase" to full open access publishing. In relation to this point NPG state that there is continuing demand from authors for traditional subscription publishing, and that Nature Communications as part of a portfolio of publishing options for authors.
The press release can be read here.