Here's where we stand. Amazon (NASDAQ:AMZN) topped the billion-dollar sales mark for the third consecutive quarter. Maybe you expected it over the holidays -- all those shoppers clicking away between the yule time Ho, Ho, Hos. And maybe a good number of neglected gift certificates bled into the March quarter, too. But we're well into retail's seasonal dead zone; shouldn't Amazon be pulling over for a breather?

Let's face it, this Amazon is legit. The leading online retailer silenced most doubters quarters ago with its profitability and ascension to the role of virtual landlord over brick-and-mortar giants like Target (NYSE:TGT), Toys "R" Us (NYSE:TOY), and even rival Borders (NYSE:BGP). Amazon, the stock, has nearly tripled over the past year.

This latest triumph -- a 37% jump in sales to $1.1 billion -- isn't about convincing doubters. It's about emerging as a non-seasonal, year-round retail juggernaut. Consider, Amazon moved 1.4 million copies of Harry Potter's new book in a single month. Now consider how that magical $25 million in sales gets lost in a $1.1 billion quarter.

From here, Amazon is looking to ring up between $4.9 billion and $5.1 billion in sales this year. It would take 50 Amazons to equal the global tally of Wal-Mart (NYSE:WMT), but to many investors, that's not the point. How many billion-dollar retailers can grow even half as quickly as Amazon is right now?

Management didn't offer bottom-line guidance, but it does expect operating profits of between $215 million and $255 million this year. With a market cap approaching $15 billion, multiples remain high by most valuation metrics. Still, the company continues to do the right things like trimming its costs and turning its inventory over faster.

That Amazon bears watching is something the competition knows all too well. This month Barnes & Noble (NYSE:BKS) has decided to ape Amazon's free shipping strategy for online orders over $25. That gets me thinking: If I buy one share of Amazon, I get the shipping free; I'd have to buy a dozen shares of (NASDAQ:BNBN) to get that same deal. Have I stumbled upon a new way to value stocks?

David Gardner argues that certain great stocks invariably trade at rich valuations. That's one reason Amazon is one of this top picks in Motley Fool Stock Advisor. What do you think?

Is Amazon here to stay or is it still vulnerable? Will Barnes & Noble's online store succeed now that it's mirroring Amazon's free shipping policy? Can you really buy one of those cool Segway scooters on Amazon? All this and more -- in the Amazon discussion board . Only on