Shoppers armed with smartphones are threatening the sales of brick-and-mortar retailers, reported the Wall Street Journal.

Smartphones allow people shopping in brick-and-mortar retailers to quickly and conveniently see how much the products displayed there cost in competing (often online) stores.

For example, if a shopper finds an item in a Barnes & Nobles, he can quickly see how much it costs at Amazon.com. If it's cheaper, he can buy it online from Amazon.com on the spot while standing inside Barnes & Noble.

Recently, Amazon.com even released an app that allows iPhone users to scan bar codes, take pictures of items on shelves or describe products by speaking into their devices, to see whether [Amazon.com] can beat the store's prices, reported the Wall Street Journal.

If online and brick-and-mortar retailers are now competing solely on price, online retailers have the advantage because they usually have lower overhead costs.

Of course, online retailing has existed for years and die-hard bargain hunters are already in the habit of searching for cheaper prices online even before the invention of smartphones.

However, the introduction of smartphones in the equation has the biggest impact on the marginal bargain hunter who is too lazy to go home and check prices online on his home desktop but not too lazy to take our his iPhone and simply scan a bar code.

The Wall Street Journal also pointed out that shoppers with smartphones may search for product information on their phone instead of talking to a sales representatives who traditionally try (and succeed, in many cases) to induce customers to buy more than they would have bought if left alone.

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