I’ve personally witnessed that Jarrod Bailey, ‘Science Director’ of the antivivisection group Europeans for Medical Progress, is fond of that dubious practice, self-citation (see below for details).

An excellent paper in ‘the journal of unlikely science’, Null Hypothesis, lists some of the reasons people self-citate:

Self-citation references can also be used to (i) let journal reviewers and referees know who has written the paper (which may not always be a good thing!), (ii) to establish to readers your reputation in a given area and/or (iii) satisfy cravings to see your name in print! In this short article I aim to examine the art of self-citation in academic writing and give some effortless hints and tips.
Professor Mark Griffiths; Self-citation : A practical guide; Psychology Division, Nottingham Trent University, UK; Null Hyp. ‘Best Of’, pp14-15

Prof Griffiths then goes on to give tips for successful self-citation, although warning that:

Those experienced in self-citation will often sink to even murkier depths. For instance, self-citation is an excellent way of introducing something that seems implausible into your argument. Two common ways to disguise implausibility is the liberal use of such phrases as “paper forthcoming”, “manuscript submitted for publication”, “internal report” or “personal communication"

Such phrases as these have been heard to trip gaily off Bailey’s lips, entering my shell-like ear at a debate at the House of Commons last year.  Jarrod referred to a ‘forthcoming paper’ - authored by him, along with published papers also authored by him!  Unfortunately for Jarrod, the journal’s editor has since distanced himself from those published papers, stating in an email that they were reviewed by;

"an antivivisectionist, Claude Reiss, in the editorial board who did some of the editing,” Parvez said in the Email.  “After his 2 years stay in the editorial board, he did lots of harm to the journal and we all forced him to resign.”
... When contacted by The Scientist, Parvez said via Email that the journal wanted to provide a reasonable opening for discussion of alternative testing methods, but also to encourage science and not polemic. “The insertion of Claude Reiss in our journal remains a very painful event.”
The Scientist, Stephen Pincock, ‘Scientists call for retractions’, 2nd March 2006

Ouch.