Aside from the time requirements (30 weekends per year would likely be challenging for many people with families), there's also the opportunity cost to be considered. If someone spends $50K over a year or two on MR's (1M miles at .05 CPM), that's money that could have been invested and earning significant dollars over their lifetime. Unless someone is already wealthy enough to consider $50K pocket change, I'm having difficulty seeing this as a wise "investment".