I've recently taken Red Mercury off sale at Smashwords. Much as I like the site, and the distribution to other places it gives you, my sales through it have never amounted to more than 5% of what has been shifted through Amazon.
By delisting the book on other channels, it makes Red Mercury eligible for the Amazon KDP Select programme - allowing Prime members to borrow the book, but more importantly, allows me to set up promotional periods when I can make my book free.
With regular sales slowing down now, I'm keen to give the book a bit of a boost with some more promotional support. KDP Select seems just the tool to do it with, so unfortunately the Smashwords listing had to go for the moment.
I will get the first promotional slot set up and let you know how it goes.