From The Guardian‘s Ten ways self-publishing has changed the books world:
The copy editor, a traditionally marginalised figure, is now in strong demand. If you are well-connected through social media, can isolate what your writing has to offer and get the message noticed by a reading public, you can probably manage the marketing of your work. The one thing it’s really hard to do is self-edit. Long ago publishers outsourced copy editing, relying on the freelance labour market – and freelancers are now being actively sought by self-publishing authors too. The price for services for which there is both high demand and scarce supply tends to rise.
It was only a couple of years ago that typos abounded in both print and electronic books. I’d be interested in seeing recent data on whether or not quality has improved since 2011, as well as how much of copy editing is outsourced by publishers. But at least it sounds like editors are being valued more — maybe this is what editing making a comeback looks like.