Nice article Grant. If I may, I would add that legally companies can only provide dates of employment and position held by the former employee. As for the reference check, let's remember that the candidate has provided references of people whom s/he knows will speak positively about him/her. While a reference check should not be ignored, one needs to be ready to ask the right questions and... listen to both what is and what is not said! Most of the time, the key is in what is not said. To hear that, you must listen attentively.
One thing that I would add (and which I did with great effectiveness as a CEO) is to ask of a candidate what is his/her passion. If s/he can't answer that, then I would question how well that person knows him/herself and whether they can therefore really perform optimally in the job. If they answer the question, it may reveal that despite the education, resume, experience and references, they are better suited to a different position.