Happy anniversary, Amazon (NASDAQ:AMZN)! On this day 15 years ago, the ubiquitous e-tailer raised $54 million in its initial public offering.

As we all know, AMZN turned out to be one of history’s greatest IPOs — on par with companies like Cisco (NASDAQ:CSCO), Apple (NASDAQ:AAPL) and Microsoft (NASDAQ:MSFT) — in fact, had you invested $10,000 in the shares of Amazon.com at the time of offering, you’d be sitting on about $1.2 million today.

There were at least hints of that kind of success when Amazon.com came public, as the company reported the following for its revenues:

Nice trend, huh?

Still, just as is common with any company innovating an industry, Amazon had its skeptics. And just as is common with any company operating at all today, Amazon still has its skeptics. (The more things change, the more they stay the same, right?)

That said, a few things did change through the years — namely, the problems the company faced. Let’s take a look at what some investor concerns from back in 1997, and how the landscape has shifted today:

1997 Worries

Losses: Since its inception in July 1994, Amazon.com had an accumulated deficit of $9 million. Sure, it seems like a laughable worry today, but during the mid-90s, it wasn’t common for money-losing companies to come public.

But Amazon.com even indicated that the losses would likely continue for quite some time after the offering. The S-1 stated:

“Accordingly, the Company intends to invest heavily in marketing and promotion, site development and technology and operating infrastructure development. The Company also intends to offer attractive pricing programs, which will reduce its gross margins. Because the Company has relatively low product gross margins, achieving profitability given planned investment levels depends upon the Company’s ability to generate and sustain substantially increased revenue levels. As a result, the Company believes that it will incur substantial operating losses for the foreseeable future, and that the rate at which such losses will be incurred will increase significantly from current levels.”

Competition: When Amazon launched, the Internet already had a field of online booksellers, including Book Stacks Unlimited and CUC International. But the big concern was that bookselling heavyweights Barnes & Noble (NYSE:BKS) and Borders would launch their own sites. With their brands and distribution footprints, they were seen as significant threats.

And even though it didn’t pan out that way, other perceived rivals at the time included Microsoft (NASDAQ:MSFT) and AOL (NYSE:AOL). Back then, many people believed these companies and other titans would dominate the entire virtual world.

Growth Potential: We know the answer today, but the unknown back then was whether ecommerce would be able to attract more and more users, or if it would end up being a sci-fi dream or even just a fad.

Interestingly enough, Amazon.com’s S-1 hinted that the company was considering expanding beyond the book-selling market. Of course, that sounded like a big risk, too. Would expansion overextend the company? Or would the Amazon.com brand be enough to carry ventures outside of books?

2012 Worries

Valuation: This has been a big issue with Amazon for much of its publicly traded life. Still, optimism continues to run rampant, and Amazon constantly finds ways to prove the critics wrong. Nonetheless, Amazon’s price-to-earnings ratio — currently 182 — is a number too big to ignore.

Competition: A problem that forever will stand the test of time. While Amazon.com is the dominant brand leader in e-commerce, it is far from safe. If anything, the industry is seeing lots of innovation. For example, Groupon (NASDAQ:GRPN) has built a billion-dollar business by reinventing the coupon business for local merchants. As for Amazon.com, it has had a tough time getting traction in the space — whether through its own efforts or its investment in LivingSocial.

Ecommerce also is seeing innovation with the user experience. Sites like Fab.com and One Kings Lane have immersive websites and mobile apps, which have resulted in high growth rates and customer loyalty. Amazon.com, on the other hand, seems more like an unexciting throwback to another era.

Not to mention, since Amazon got into the tablet business with its Kindle Fire, it threw its hat into a ring that includes Apple, Samsung and Barnes & Noble — and ironically, it might have created a pressure point that brick-and-mortar retailers Best Buy (NYSE:BBY), Target (NYSE:TGT) and others can exploit.

Expenses: The costs of running Amazon.com always seem to increase. Last year it built 17 massive fulfillment centers, and it also had a 67% spike in headcount to 56,200. The result — coupled with selling Kindle Fires at cost or worse — is ever-shrinking operating margins, which are about 1.5%. True, that’s not a problem if you’re growing revenues, but eventually, Amazon.com will start to see its top line flatline.

Verdict

Looking back at the Amazon.com IPO, there are some important takeaways.

AMZN was smart by establishing a footprint in books, as it gave the company a way to test the market and understand the key drivers. From there, it was easier to replicate the model to other categories. Amazon also understood that building a strong infrastructure was absolutely crucial. In a way, it always was investing ahead of its growth. Plus, the company continued to keep its focus on innovation, having developed the aforementioned Kindle and Kindle Fire, as well as an affiliate program and even a cloud platform.

But perhaps most importantly of all, Amazon.com ended up hitting a big need in the market, which was reflected in hyper-growth in sales.

Looking back, Amazon might have been expensive even 15 years ago — but looking back, it was so, so cheap compared to its long-term potential.

Tom Taulli runs the InvestorPlace blog IPO Playbook, a site dedicated to the hottest news and rumors about initial public offerings. He also is the author of “The Complete M&A Handbook”, “All About Short Selling” and “All About Commodities.” Follow him on Twitter at @ttaulli or reach him via email. As of this writing, he did not own a position in any of the aforementioned securities.