Is (NASDAQ:OSTK) undervalued, or is (NASDAQ:AMZN) overvalued?

In the weeks since Overstock CEO Patrick Byrne pointed out the disparity between the valuation of Amazon and that of his own company, investors have been riding the Overstock rocket. On Feb. 13, the shares closed at $18.15, and have since climbed to $27.69.

Yet, the disparity persists. As I write, Amazon's $17.3 billion market cap is nearly 37 times Overstock's $470 million. Meanwhile, Amazon posted fourth-quarter revenue of $1.95 billion, or about 15 times Overstock's holiday season sales.

Asked if he meant to imply that Overstock is undervalued, Byrne -- who has been buying shares on the open market himself -- said this in an interview on The Motley Fool Radio Show: "Well, I can't say anything like that. I just hope Amazon goes to $100 billion in valuation because it is just going to be good for us."

Well, I don't know if I would have put it quite that way. I'd like to think Byrne meant that he hopes Amazon will actually be worth $100 billion someday. But to hear Byrne say it, something's gotta give. Either Amazon, the old Rule Breaker, has to come down, or Overstock, the Motley Fool Hidden Gem -- has to go up.

Investors have questioned Amazon's valuation in recent months, and the stock has dropped about 25% since the company released its fourth-quarter earnings last month. But right now, it is more reasonable at 50 times trailing free cash flow and 45 times this year's earnings.

If Overstock is truly viable, and if Patrick Byrne is right, this stock may yet have a ways to go.

Owning Overstock has been particularly exciting for those who found it early. You can try Motley Fool Hidden Gems freesimply by clickinghere.

Fool contributor Jeff Hwang owns shares of