At a time when Amazon.com (NASDAQ:AMZN) and Barnes & Noble (NYSE:BKS) are shipping most media orders of $25 or more for free, the new May promotion for Overstock.com (NASDAQ:OSTK) may not seem like much. The company is reducing its already cheap $2.95 flat rate shipping to a round $2 all month long.

With revenues up by 102% this past quarter, it's hard to argue with the company's marketing ability. But still, one has to question whether this is a sound practice storewide.

For example, strolling through the site I found a solid pine queen-size bed. The list price of $989 really can't be taken seriously, but the site's price of $389.99 appears to be a pretty good deal. I think it's safe to say that shipping this gargantuan bed will run the company far more than $2.

A few months back, I took advantage of the company's dirt-cheap shipping to buy a bulky, king-size foam mattress, while a fellow Fool recently bought an 80-pound rug from the popular closeout and clearance site.

I mean, I still feel guilty about taking advantage of Amazon.com and its partner Toys "R" Us (NYSE:TOY) for free shipping on lawn furniture and a heavy backyard trampoline. Yet those purchases were made years ago, when online companies were concerned only with growing the top line, and asking about profit margins came later.

I'm a fan of Overstock.com. It's trading for less than when our Rule Breakers newsletter service singled it out back in October, and the discount makes it ironically tempting -- Overstock.com? On sale?

The problem here is that the company's emphasis on sales growth has come at the expense (pun intended) of profitability. Over the past three months, analysts have gone from pegging the e-tailer's earnings potential this year from a profit of $0.34 a share to a deficit of $0.24 a share. Wall Street's forecast for 2006 has been pruned to a profit of $0.62 a share from a $0.92 a share showing in that time.

Then again, perhaps some opportunistic investors may be grateful for the company's fiscal shortcomings. Just as our Rule Breaker subscribers have learned to embrace companies that flow against the current of conventional wisdom, Overstock isn't just making customers happy at the expense of its income statement these days. Keep in mind that Amazon.com spent many of its formative years operating at a loss. It helped the company grow its faithful audience. When the time was right -- and that day may come for Overstock -- Amazon.com simply limited its cheap shipping promotions to light items like its flagship books and CDs.

So I get it, Overstock. Keep the deals flowing. Get the buyers to become lifetime fans of your overstocked merchandise, travel deals, and consumer auctions. Excellent. Just don't lose sight of the bigger picture down the road.

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Longtime Fool contributor Rick Munarriz has been a shopper at Overstock.com a few times in the past -- and likely even more in the future. He does not own shares in any of the companies mentioned in this story. The Fool has a disclosure policy. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early.