Blue Nile (NASDAQ:NILE) recently reported better-than-expected quarterly earnings and raised guidance for the rest of the year. Shares of Blue Nile have more than doubled over the last six months. Can the online jeweler continue to deliver for investors? Will Tiffany (NYSE:TIF), Overstock (NASDAQ:OSTK), or (NASDAQ:AMZN) take a bite out of Blue Nile's business? In this installment of "Fool Video," I ask Motley Fool senior analyst Rick Munarriz.