Here's a chart that provides a snapshot of the state of flash sales sites' traffic.
As you can see, the best performing company of the bunch is Zulily, which is filing for an IPO. The worst of the bunch is Fab, which has raised a lot of money.
When reached for comment, Fab said, "In e-commerce, especially at Fab, it's about quality of customers, not quantity. And we are VERY happy with the quality of our customers (they're buying, repeatedly)."
Overall, the traffic to flash sales sites isn't looking particularly good, aside from Zulily.