Paul Smith over at Welcome to the Occupation has posted is list of why HR isn't the most popular group in an organization. And they are:

10. HR can be cold-hearted. 9.   HR is too touchy-feely; Emotions have no place in the workplace. 8.   Employees are not categories or rating scores. 7.   HR cannot develop the perfect performance evaluation system. 6.   HR thinks they're above it all and rules don't apply to them. 5.   HR creates bureaucracy. 4.   HR doesn't generate revenue. 3.   Anyone can do HR. 2.   Few do it well, because... 1.   It's hard work.

Source: Welcome to the Occupation