Thickness planer blade nicks
Long story short, I decided to trace the cause of those annoying nicks in my planer blades today, while planing some soft maple and birch. I expected them to be from bits of sand from the shop, sandpaper, dirt caught on the stock, etc. Every one came from a pitch pocket in the wood; each new ridge in the surface, indicating all 3 blades had gotten nicked, started at a black pocket in the wood.
Given that blades, blade sharpenings, and labor are all more expensive than a few board feet of soft maple, it's a significant incentive to be careful about what goes through the planer, at least with any sort of sharp/clean blade in it.
Maybe it's common knowledge, but I thought I'd share my experience.