I recently had one of my images used in article that was posted to LinkedIn and Academia.edu (one of the articles has since been removed) without giving proper attribution. What is ‘proper’ attribution? On the bottom of each page of this website is my Creative Commons license: BY-NC-SA (attribution / non-commercial / share alike). The license is simple and has stood the test of courts in many countries.
If you are going to use some writing or an image from the Net, it is best to first determine its provenance. This source is not usually Google, which is merely an index. I suggest following the advice of Kate Hart, on Citing Sources [note the name & link]: “in general, the reason the internet has images at all is because of ‘fair use.'” This is known as ‘fair dealing‘ in Canada, and copyright laws are different around the world. It is best to be informed.
In general, giving attribution to the originator is the minimum requirement. Nina Paley, creator of the Mimi & Eunice cartoons, sums it up well in this animated video, via QuestionCopyright.org. Just remember, “Proper citation will make you a star“.