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If there's a theme emerging from the summer tech earnings season, it's that Apple's (Nasdaq: AAPL) iPhone is equal parts enabler and destroyer.

Need proof? You'll find it in the Mac maker's blowout earnings report. The iPhone brought in $13.3 billion in revenue as sales more than doubled to 20.3 million units, which means prognosticators who had called for 15 million to 17 million in unit sales are probably cleaning out their desks. This is the iEmpire at work, Fool.

The crust is shifting!
Like a massive earthquake kicking off an endless wave of aftershocks, the iPhone is changing the fortunes of virtually everything it touches -- for good or ill. Here's a closer look at three companies whose earnings either suffered (or benefited from) the iPhone's influence.

1. AT&T (NYSE: T)
The former Ma Bell booked $31.5 billion in second-quarter revenue, up 2.2%, and per-share earnings matched last year's $0.60. Overall wireless revenue improved 9.5%, and wireless-data revenue -- an essential element of smartphone plans -- grew 23.4%. AT&T activated 3.6 million iPhones during the quarter, with 24% of those customers new to the carrier.

Handsets using Google's (Nasdaq: GOOG) Android operating system accounted for 40% of the 5.6 million smartphones AT&T sold during Q2, but the large number of iPhone activations suggests that the robot is more alternative than replacement -- though both could very well be cutting into sales of Research In Motion's (Nasdaq: RIMM) BlackBerry.

2. Nokia (NYSE: NOK)
Or maybe the former Finnish phenom is the iPhone's primary victim, since Apple has passed Nokia as the world's largest smartphone supplier. Profits have suffered as a result. Last night, the company reported a net loss of about $530 million (368 million euros) as revenue declined 7.3% on a 34% drop in smartphone shipments. Remember that deal with Microsoft (Nasdaq: MSFT)? Yeah, it isn't helping yet. Investors sold the news, and the stock is down more than 3% as of this writing.

A rally may not be in the offing. During yesterday's conference call with analysts, CEO Stephen Elop referred to a "shift in the product mix" toward cheap devices as a leading cause of Nokia's poor Q2 performance. The implication? Once the smartphone leader, Nokia is rapidly becoming the king of feature phones. That may be fine for a low-cost Asian manufacturer, but not for one of Europe's largest companies.

3. Verizon (NYSE: VZ)
Big Red put up Big Numbers in Q2, thanks in large part to subscribers who were hungry for its iPhone. The company activated more than 2.3 million iPhone 4 handsets on the way to booking $0.57 a share of earnings on $27.5 billion in revenue. Analysts had been calling for $0.55 and $27.43 billion, respectively.

The numbers could continue to improve. Since February, when Big Red's iPhone first went on sale, Verizon has activated 4.5 million Apple handsets. "Sales have been steady, and in fact, [the iPhone] is one of the top-performing phones on our 3G network in terms of voice quality, with the least number of dropped or lost calls and high overall customer satisfaction," CFO Francis Shammo said during this morning's conference call with analysts.

Steady sales. Top performer. Customer satisfaction. This is the iEmpire at work, Fool. For investors, the iPhone opportunity looks richer than it ever has.

Do you agree? Which of these four stocks would you use to bet on the iPhone? Seriously, I'm asking. Please vote in the poll below and then leave a comment to tell us what other ways the iPhone will affect the market. You can also add all four of these stocks to your watchlist for up-to-date analysis as soon as it's published.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.