Although that did happen, but I think that was the recruitment agencies: they'd debrief their candidates after their interviews, and the next time they sent someone in, they'd be prepped for the whiteboard design exercises we'd used previously. I ended up with a dozen different questions that I rotated, which seemed to be enough.
General interview questions were often prepped too. Our phone screen question list had to grow quite long before it seemed like the effort to cram/prep was too much trouble.
