Why is it so hard to both find work, and find good candidates for work?

I came across a webcast the other day of an interview with Peter Cappelli from the University of Pennsylvania's business school, where it was being discussed that it is employers who are to blame for the "skills shortages" that we see happening in many industries, and which in my own personal experience in particular is felt quite strongly in the IT industry.

In his interview, Peter makes some really good points about how the human resources departments in many companies have either shrunk or been made effectively obsolete, essentially removing some of the more traditional checks and balances in the recruitment process. He also mentioned how most companies put very little effort into providing skills and training any more, and how the modern screening processes where aptitude tests and applications asking lots of yes-no answers can result in finding no suitably "qualified" applicants out of a pool numbering in the thousands!! It's these last points that I feel are the most telling, and in particular when the modern day hiring processes that most companies seem to use (referred to as the Silicon Valley model) seem to embrace a zero-training + blind-screening process (a subject I have touched on before).