Overstock (NASDAQ: OSTK) is throwing in the towel. Less than six months after announcing a strategic shift aimed at slowing Wayfair's (NYSE: W) growth in market share, the e-commerce retailer has abandoned that approach. And, in scaling back its marketing spending and price cuts, Overstock is essentially admitting that its competitor's impressive growth rates aren't so easy to replicate.Wayfair and Overstock target the same demographic of mostly younger shoppers who are open to ordering home furnishings online.