InfoWorld's cover story is "The Top 20 IT Mistakes," and it's a rogues' gallery indeed.  Amusingly, many are the converse of another:  For example, "botching your outsourcing strategy" vs. "offshoring with blinders on." 

The moral I take away is that many of these are not "IT" mistakes—they're people mistakes.  Ones like "discounting internal security threats" are obvious enough; depending on whether you believe Gartner, 70% of security incidents involving an actual loss are inside jobs.  But others, while less blatant, are still at bottom people issues:

• "promoting the wrong people:"  Well, sure; don't assume your top technologist deserves or wants a management position.
• "mishandling change management:"  Change is a constant, but so is people's resistance to same.  You must anticipate this and bake it in to your project planning.
• "mismanaging software development:"  Which most frequently occurs when frustrated IT managers throw more and more of the "mythical man-month" at a tardy or delayed project.  The solution instead is to find better programmers; "almost nothing else matters, really."
• "letting engineers do their own QA:"  Res ipsa loquitur.

I recommend you read it all—and this goes double for those of you in the audience who are not in IT management.  This is a devil you need to know.