One of the last week's biggest losers was Vipshop Holdings (NYSE: VIPS), shedding 22% of its value after posting disappointing financial results. At least three analysts would go on to downgrade the stock.The online discounter of brand-name apparel in China has fallen on hard times lately. The stock closed out last week by hitting new 52-week lows in four consecutive trading days, a streak it can extend to five by Monday's close if the sell-off continues.