Math research or anything new/clever in a particular niche. Imagine you optimized a piece of code to get an advantage or came up with some clever trick to solve a common problem in your niche and then everyone gets it from free from Claude believing, as you pointed out, that it's now their work.

I had this exact conversation with my business partner a few days ago. Our "secret sauce" might not be worth that much after many years but still I am not comfortable exposing it to Claude. Fortunately it's very easy to separate in our project so Claude gets the other parts and is very helpful.