The "big is beautiful" era of American consumerism may be over. Many companies known for their gigantic presences now seek to leave daintier footprints on the retail landscape. If you hold big-box stocks, this adjustment might prove painful for your portfolio.

Best Buy (NYSE: BBY), known for its mammoth locations, plans to reduce its square footage by 10%, shutter some stores, and more aggressively open smaller stores that focus on the popular smartphone market.

The company's strategy includes opening 600 to 800 Best Buy Mobile stores in the next five years. Aggressive expansion of Best Buy Mobile sounds like a major threat to RadioShack (NYSE: RSH), which has long kept afloat by peddling mobile phones.

Best Buy's not the only company eyeing growth by shrinking its stores. Wal-Mart's (NYSE: WMT) name is almost synonymous with "behemoth," but it's also been talking about a strategic shift to smaller stores.

Warring on the Web
Dot-com bubble predictions that online shopping would devastate or entirely replace bricks-and-mortar stores may not have come true immediately, but they weren't necessarily wrong. E-commerce powerhouse (Nasdaq: AMZN) has grown to become a major rival for its physical counterparts, and its intense competition has helped to grievously wound real-world competitors such as Circuit City and Borders. You can also see the influence of Amazon and other online stores in Best Buy's move toward offering a larger selection of electronics items online.

Though Best Buy seems to have its big-box back to the wall at present, long-term investors still might not want to rule out this stock idea. It currently trades at just about 10 times earnings, and its PEG ratio of 0.81 implies it's a bargain. It may take awhile for Best Buy to get its groove back, but I doubt its future prospects are as grim as everyone seems to believe right now. Plus, the company's clearly willing to try to change its ways to adjust to changing times.

As for the overall big-box model, perhaps we're simply running out of room for them. Their massive footprint arguably doesn't help them dodge attacks from smaller, nimble competitors, either. To stay alive and keep growing, many retailers are being forced to think outside their big boxes.