I think of it more as a continuum that either full due diligence or hire most anyone who seems decent.

I agree that the latter version is wrong, but there is room to adjust how much you work on predicting future performance. How much of a jerk people are is one of the harder things to predict in interviews.

I get the feeling we're both speaking with previous unfortunate experiences in mind :)

The only thing that makes this hard, is when you spend a month looking for a viable candidate, and need work done, and have to pick someone... The person isn't your ideal choice, but the best of those available. It'll work out, or it won't.

In general, I tend to prefer people who are able/motivated to learn, as opposed to X years of experience in keyword Y.

Sure. You're going to have to hire someone and there's always some risk that it won't work out.