The way I see it, the ecosystem cycles through buying Bitcoin to be spent at Overstock, and Overstock selling it back to someone else, and then someone buying or using Bitcoin to spend it back on the site again. Overstock's circulation is very good for Bitcoin, and I highly doubt its hurting it. Its causing more buys than hurtful sell pressure.

Like others said, it is certainly speculative by the looks of what is currently draining the price.