To continue the dating analogy, you don't just get married after a romantic dinner for two (unless, perhaps, you're a celebrity); you 'test drive' the relationship first. You also, hopefully, maximise chances of success at bringing up kids, sharing finances etc, by getting a chance to learn the other person's values and attitudes.

This seems to me bang in line with the 'give an interviewee some real work to do' school of thought. I do wonder why so few types of jobs involve a trial or probation period, though; perhaps due to mistrust? When you start dating someone, you're not committing to the next n years with them, yet when you join a company, you kind of are.

I've seen from MMO guild leadership that having a trial period can really help stop significant problems further down the line (although, unfortunately, not always). Yet I'd not consider hiring an employee, at least in the software dev world, on spec (i.e. the 'do some real work' part of the interview is actually the start of the job). The only intermediate is perhaps contracting someone first, then bringing them on fulltime. I wonder how customs have evolved this way; respect for other people's need to pay the bills? Desire to minimise short jobs, churn, and to maximise the ability to seek new jobs while still in one? Hmm.