The worst filter is choosing at random. If I shuffle a stack of resumes and throw half in the trash, I have eliminated the unlucky candidates. I have certainly rejected a good number of skilled and highly qualified candidates. Regardless the filter did its job, I have fewer applications to review.
If I give candidates whiteboard problems, I filtered out thoughtful people who don’t perform well under pressure. If I look at interviewees github submission and blog posts I have filtered out intelligent people with a dearth of free time. If I combine the two filters with an OR relationship, I now let more people through and have a filter that is less effective at narrowing down candidates.
All filters filter out good candidates. Anyone who finds a way to find exactly the right candidates from a filter in a way that isn’t bespoke and is scalable is going to be very successful.