Yeah, sorting out serious people from those wasting time is a hard one. Though I'm generally pretty sympathetic to employees/candidates on that one - am I wasting your time if I'm pretty sure I don't want to leave my current place, but want to keep a hand in and know what the market looks like? I would say know, but I know some people who would disagree, and have decent reasons for it.

Even after that, the "experience candidate phone call to see if they're worth flying in" part is definitely the one where I have the hardest time, being not in the Bay Area. I was lucky to find some great local people, where the cost was lower, because that's an expensive one to have to get good at fast. You lose a lot of nuance over the phone, though some other people in the company have been having very good luck with homework in this case - but as a candidate-choice option, where they could still go the traditional route if they wanted.