I'm interested in the common practice in commercial settings (I have a small home-cooking business, and I want to align myself with the norm in restaurants etc..)
Since this hasn't specifically been addressed yet, I'll throw in my experience in industrial kitchens/restaurants.
Plastic spoons. Hundreds of them. Thousands of them. Literally.
We had a bain marie at every station. At the beginning of every shift, it was re-filled with plastic spoons. Each station had their own box of spoons to refill throughout the shift. Every single dish was tasted at every single stage with a plastic spoon, which was then thrown out. I would say that I went through ~150 spoons on an average shift, god only knows how many when we were busy.
Purchased in bulk, the cost wasn't prohibitive. I would hazard a guess that a box of 2500 plastic spoons cost us about 30 USD.
While it might seem wasteful, the cleanliness/health payoff was worth it. I don't want to name names, but this was a multi-national, multi-billion dollar hotel chain (4 star/4 Diamond) and we had a third party come in and audit us 1-2 times a year, in addition to the Health Department. Both the third party and the Health Department had the authority to shut everything down at a moments notice if they didn't like what they saw. I don't know the statistics for the Health Department, but the third party rated our kitchens (we had three) in the top 10 cleanest operations in North America (within our company) more than once.
We also recycled the spoons, so there's that as well.