That would only be a risk if we were talking about a typical high school multiple choice test. I would think that a cheater would be filtered out by this point in their career (this point being applying to a high tech company). However, collaborating on a solution is not necessarily a bad thing. I think the goal here is to find candidates which can deliver unique, valuable, and insightful problem solving skills. To go ahead and bottle that process up into a pre determined steps or a 1 hour drill doesnt serve your goals very well. Who knows, maybe these guys have a recipe which works for them. From my own experiences, I would disagree.