A couple of weeks ago I gave a departmental seminar on my current research. Afterwards, one professor approached me and had a "professional request" as he called it. He requested that I cite a paper that he was a coauthor of. I did a thorough literature review of my topic. His paper did not come up in my search.
There is a huge difference between telling someone about a paper and saying "Take a look at this, it might be helpful" and saying to a graduate student "Please cite my paper." Just another example of the character, or lack thereof, exhibited by members of academia.