Hi Satan,

(Note this answer deals with the word guru in the meaning of a charismatic religious leader, it does not deal with the word guru in the meaning of traditional Hindu family preceptor who also performs rituals etc.)

The problems and risks of the guru devotion and the guru-disciple relationship have gradually become uncontested, at least here in the Netherlands. (source among others "The Volkskrant" and Andrew Cohen's magazine "What is Englightenment")

First , to attract disciples and to acquire their devotion the guru must present himself as pure, saintly, fulfilling ancient myth or prediction, or enlightened. Of course, there are only few if any who are really pure, saintly etc. In other words, most gurus lack authenticity. This will invariably lead to disappointment and devastation. (source among others "The Guru Papers")

Second, gurus have often a lot of authority due to their status with no checks and balances. Of course, in many cases this leads to exploitation and abuse of power and sometimes also to the acceptance by the disciple of misguided advice of the guru.  (source, among others Anthony Storr)

Third, most gurus surround themselves with sycophant inner-circle people. This will corrupt and degenerate most gurus. (source among others "The Guru Papers")

Fourth, the teaching of the guru are not open for investigation, it all hinges around the reliability of the guru that are often uncritically accepted by the committed disciple. This of course, has the very big danger of leading people into false teachings and a fantasy world and harmful or dangerous practices. (source, among others John Horgan and Robert Priddy)

Most disciples think of course that this happens with other people's gurus and other people, but it can easily happen with you and your guru. (Source my own observation and experience)

http://www.american-buddha.com/myth.guru.htm#THE%20MYTH%20OF%20THE%20TOTALLY%20ENLIGHTENED%20GURU aticle by John Horgan (requires sign up)

Andries Krugers Dagneaux  (amateur guru-ologist)

(minor modification in contents)