How to address the issue of the widespread use of protected material in informal publications?
From an ethical point of view, I think most people can still sleep well despite taking the first fish from Google from time to time. 

From a legal perspective, it depends on your jurisdiction and the license of the image. As Jeff points out, it's often fine in many places.

You should define your goals (ethics vs. legal), and act accordingly (which is my case would be do nothing).