Who to hire

A colleague mentioned to me the other day that he prefers to interview people who are currently unemployed. When I asked him why, he explained that they’re more eager to negotiate and more likely to accept an offer than someone who is currently employed.
You can most certainly fill an open position faster by interviewing unemployed candidates but you’re less likely to hire the best candidate for the job. A candidate who is already bringing home a paycheck generally has a greater ability to consider the suitability of the job than a candidate who needs that paycheck.
In general, I think that hiring the best person is probably of greater importance to the company than filling an opening quickly.
What do you think?