Couldn't a large proportion of resume spam be filtered just by asking the applicant for something specific, and ignoring anyone who doesn't comply? IE. Add a sp

Couldn't a large proportion of resume spam be filtered just by asking the applicant for something specific, and ignoring anyone who doesn't comply? IE. Add a specific phrase to the subject of the email. You could embed this in the middle of the job spec; people whom don't read it carefully are likely not worth interviewing anyway.