Despite airing a retro-themed commercial during the Super Bowl that turned out to be a lot of self-deprecating fun (during an evening full of self-important, serious ads), RadioShack is not seeing a bump in business. The company just announced it would close about a fifth of its locations.

This still leaves RadioShack Corp. with a surprising number of retail stores across the country: more than 4,000 RadioShack stores, including 1,000 franchisees, according to the Wall Street Journal's report, will still be open for business after the company's deep cut of as many as 1,100 locations.

RadioShack also disclosed that some of its suppliers are demanding letters of credit, totaling around $67 million, to guarantee payment, but the company said it had enough credit and cash to cover its business this year. RadioShack reported a total of $191.4 million in losses during the holiday season, with a revenue drop of 20 percent to $935.4 million.

RadioShack's Chief Executive Joe Magnacca attributed the company's woes to a drop in the number of shoppers coming in to the store, along with heavy competition during the holiday shopping season and lower than expected sales of mobile devices and accessories, which RadioShack normally relies on for about half of its sales. Operational flubs during the holiday season, like inventory problems, also contributed to the company's weak showing. "Simply put, we exceeded our organization's capabilities by trying to do too much too quickly," Magnacca said, according to WSJ's report.

"Overcrowding" of RadioShack locations was also cited as a big problem, which is what led to the company's jarring decision to cut locations by about a fifth. "Within five miles of my home, I have eight RadioShack locations," said Magnacca about the move. Shares of RadioShack dropped precipitously, by 24 percent, after the company's holiday sales figures were released.

Amazon and E-Commerce

The other, and ongoing, factor contributing to RadioShack's problems is the rapid growth of e-commerce, in general, and Amazon, specifically.

Take this comparison, for example, brought to light by The Atlantic:

"In 2003, Amazon and RadioShack each had about $5 billion in sales ... Last year, Amazon had $75 billion to RadioShack's $3.5 billion ... At the end of 2013, RadioShack had 5,000 brick-and-mortar stores with 27,500 employees and $3.5 billion in sales, which is $127,000 in sales per employee. Its website is the 1,066th most popular in the world. At the end of 2013, Amazon had zero brick-and-mortar stores with 117,300 employees (full- and part-time) and $75 billion in sales, which is $640,000 in sales per employee. Its website is the 5th most popular in the world."

Of course, Amazon sells much more than RadioShack's selection of tech gadgets and DIY widgets, so the comparison isn't exactly fair.

But Amazon (and other online retailers) does offer the same gadgets and widgets as RadioShack, making RadioShack's woes an illustrative example of what's happening to any brick-and-mortar retail stores that the world's largest online retailer competes with, including the (nearly) vanished book store, electronics and small consumer goods, and, perhaps in the future, fresh groceries.

Amazon's huge selection, convenient delivery, and low workforce-to-sales ratio help it offer way lower prices than its competitors in the "real" world, and outpace them in sales year after year.

Brick-and-mortar stores are still by far the largest part of U.S. retail sales, as Business Insider showed while saying that reports of the "death of traditional retail" are greatly exaggerated.

 And almost nobody would buy a car or major household appliance from Amazon.

But e-commerce, with Amazon at the leading edge, is chipping away at the retailers it can compete with first, and RadioShack's slow death is a telling indicator of that fact: Buying a smartphone or 25 feet of coaxial cable? A RadioShack trip can get you those items today, but wait two days and you'll probably get them cheaper online.