"Defensive medicine" is a common defense but, in my limited personal experience I don't think it is valid. Doctors who know (and follow) the guidelines never seem to say anything about Defensive medicine; Doctor's who seemed to either not know them as well (or just not know what they were doing as well in general) were constantly bringing up defensive medicine complaints. Its also interesting to note the many of the tests you order come with an interpretation provided by another physician. So, a Doctor (esp. resident / intern) who is unsure of themselves will often order unnecessary tests as a way to consult with other Doctor's (it is, process wise, far too difficult to simply say "I don't know" and get help).