I have a friend who assigns one knife for cutting raw meat, another knife for cutting fruits and vegetables, another for cutting cooked meat, etc. Is washing one knife after each specific use not sufficient to avoid cross-contamination? (Note: different cutting boards are assigned for different food types as well)
Using separate cutting boards is advisable, but separate knives are unnecessary. 90% of my cutting is done with my chef's knife. I don't own two of these, nor would I use a subpar knife for the job.
I almost always find it most convenient to start my preparation by cutting the veggies, fruit, etc. first and then finally cutting the meat last. Then you can wash your knife once and be done with it.
Cutting board material is typically absorbent, whether it's wood or a knicked, scratched, sliced-up poly board. Try as you might, you can't guarantee the cleanliness of a cutting board; however, a knife blade is made of metal and doesn't retain material like a cutting board. You can therefore assure that, once cleaned thoroughly, it can be used again for different food.
I agree This is completely unnecessary so long as you clean your knives properly (soap, hot water for the blades). However make sure your knives are in good working order. Loose grommets or grooves can be great places for bacteria to hide. Personally I prefer knives with commercial grade "Sani-Safe" handles.