C Threading in real-world apps

Question

Learning about threading is indeed fascinating, and there are a number of excellent tools available to help you do it. However, my concern is threading used directly in real-world systems, either as part of design or development.

I've worked on a few well-used and well-architected.NET projects in C#, but I couldn't find any evidence of explicit usage.

Is there a legitimate requirement for this because it is managed by CLR, or is there another reason?

Also appreciated are any examples of threading coded in commonly used.NET apps found on Codelplex or Google Code.