I do something very similar in my hiring processes on odesk. I ask each candidates opinion on something (articles usually). This allows me to eliminate 90% of applicants. Then I review the 10 applicants who's answers weren't complete gibberish and give the best 2 or 3 a programming task. Works pretty well, I've only ired one guy turned out to be inadequate for the role (out of about 20 hires over the past 4 years for php dev work).