I have let book go out of the house, but not supplies. In classes I have let others borrow my rulers, cutters, thread, scissors etc. I have always gotten them back and have not had any problems. I too have had to borrow thread colors from others. For the most part the classes that I take are with the same people and we have gotten to know each other over time. The teacher also brings her supplies and loans them out. When my friends come to my house to sew, I let them use my supplies because it is easier than them carrying over their things. Of course they bring their own scissors, thread, fabric, cutter, and anything of the smaller supplies. No big deal for us.
I do not think I would be so generous if I did not know the person.