Something that blatant, in other words, where we actually see the evidence for it, is still fairly rare. What is much more common and, probably, far more common than anyone would like to admit, is pressure on authors, sometimes even from editors of journals who want to increase their impact factor—something we just heard about, of course—and so what they do is they don't quite come in out and say this, but they say.... Review recommendations go back, letters to the authors that say, “Well, we would really appreciate it if,” or “It would be better if you cited a paper from our journal,” or something like that.
Then, it gets even more complex, a little harder to track when they have these—and I used this phrase in my testimony—“citation cartels” that people actually organize as citation rings. Again, we don't know exactly how often it happens, but if you were to speak to a bunch of researchers, I doubt that any of them, if they were being honest—and I would like to think they would be—would say that they've never had an experience when someone in some way had pressured them to cite their work, whether it's a reviewer, an editor or even someone else.
This, again, is a natural outgrowth, if you will, a completely predictable response. People just respond to incentives, to knowing that you need your h-index to be higher. What's a good way to do that? It's to make sure that you are cited more often.