Nowadays, there are enormous information on the internet. We look into various websites on the internet whenever we need to know something important. In most cases, the answer to our question is found on the internet. The internet is so called a online textbook, and sometimes superior to authorized textbooks.
However, it is sometimes risky to trust the information on the internet. In some topics, online information is very inclined. In addition, there are lots of erroneous description on the internet, because it is easier to state a personal opinion without any authorization or inspection on the internet than to publish a paper article.
So, paper books and articles are more authorized than the online information, as a principle. In addition, it is difficult to correct some description in a book than on the internet. It makes us deliberative to publish a paper article.
Then, is it inappropriate to refer to the internet for writing a book? Of course not. We can utilize any information around us. Simply, we are responsible to guarantee the correctness of the information we referred to.
However, it is a little complicated in the region of academism. According to this article, academic articles in which some description in Wikipedia were referred are increasing recently.
British Medical Journal: References that anyone can edit: review of Wikipedia citations in peer reviewed health science literature
This is an academic paper reporting the frequency of citation from Wikipedia in the academic articles. The result is not surprising. Not only in some niche journals, but also in many articles published in famous journals utilized citations from online articles.
The authors warned that some description in Wikipedia can be rewritten occasionally. In such cases that the referred article were rewritten after the publication of the paper, readers of this paper who investigated the description in Wikipedia would be misled. It is far from the intention of the authors of the paper.
I agree with this opinion. However, it is not cool that we never utilize online information to avoid the risk of alteration. I believe that Information technology will solve this problem in the near future.