Amazon.com (NasdaqGS: AMZN) shares plunged on Friday, dragging down consumer discretionary sector-related exchange traded funds. On Friday, the Consumer Discretionary Select Sector SPDR (NYSEArca: XLY) fell 3.4%, the Vanguard Consumer Discretionary (NYSEArca: VCR) dropped 3.4%, and the Fidelity...