Perhaps the most important reason why referencing research and citing sources is so important is because authentic research and ideas serve as what the Grinnell College website calls the "currency of academia." Original research and ideas also provide a basis for journalistic integrity. Thus, a writer must make sure to authenticate his sources before quoting or citing research. Overly relying on Internet sources such as Wikipedia in this case can be risky, as the information presented there may be vague or incorrect.
If you write an idea without giving a source the proper credit due, then you will be in violation of that source's ownership of the idea. An un-cited idea you write will be credited as your own and thus will be seen as plagiarism, which is a serious crime. Not only must you quote your source, you must also specifically cite the original author in the correct format.
Academia not only values the currency of ideas themselves, but also the roots of these ideas, or what Grinnell College calls the genealogy of ideas. It is important to see how such ideas develop over time, so citing your original source allows readers to trace back to that source. Scholars must be able to trace the source of ideas in order to apply them correctly to current modes of thinking.
You should know which citation method to use based on what kind of material you are writing. For instance, writers of the humanities generally use the Modern Language Association, or MLA, style of citation. Historians use the Chicago Manual of Style. Students and professionals in the field of psychology will use the American Psychological Association format, and for sociology, the American Sociological Association format.