From their FAQ:
WHY NOT JUST CHARGE FOR USE? We thought of that, and in fact, it was always our plan to do so. But Editorially is a sophisticated application that requires a team of engineers to maintain and develop. Even if all of our users paid up, it wouldn’t be enough.
This essentially sums up everything that is wrong with start-up culture. When the acquisition lottery doesn't pan out, most start-ups fold. Sad, really.