Amazon offers the KDP select option which is available to any author should they go exclusively with them and in exchange, you get to offer your book free for a few days a quarter. I tried this once and it did wonders for my exposure. Within just a couple of days I had over 600 downloads. I know, I didn't get paid for it, but you have to start somewhere. In this case, sometimes just getting people to read your work is hard enough, let alone getting them to pay for something from an unknown author.
In the end, I am not really losing anything from this move. As I've said, I got no return for the work I did concerning Smashwords. For a good year my work sat there and did nothing, regardless of how much I promoted. At least with Amazon, I do get some sales there and a few reviews. That's more than I can say for Smashwords.