The Center for Media and Social Impact has recently issued a new "Code of Best Practices in Fair Use for the Visual Arts" that strives to provide a good, reasonable set of guidelines on the subject.
It can help various exhibitors and other stakeholders answer questions like: "Can an artist use images from Facebook in her collage? Can an art teacher show pictures he took at an exhibition in class? Can a museum put a collection online?"
In this digital age, there can be many questions that emerge. While I'm sure there will be some who object to the interpretations and approaches presented within the code, from what I'm seeing so far, it's mostly guided by common sense. Be sure to give it a look. What are some concerns you have, and where might it be improved?