Popular online games like FarmVille use powerful reward systems to get players to spend real-world money on virtual items. Zynga/AP hide caption

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Can You Help Me Tie My Shoe? Researchers found that when study participants were asked an unusual request, they were more likely later on to perform a favor. iStockphoto.com hide caption

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Denny's Beer Barrell in Clearfield, Penn. features a 15 pound burger for $39 that is free if the customer can finish it. Jeff Swensen/Getty Images hide caption

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