Thanks for the reply. If you are already running these private competitions it might be useful to advertise them a bit more openly (then you will need some formal criteria for joining to avoid user resentment, e.g. those in top 100). You are right that the system as is can help to find people who have some combination of persistence, general intuition for dealing with data and a modicum of modelling skills - "the world's best data scientists" is doubtful but certainly beats interviewing.