Imitation isn’t just the sincerest form of flattery — it’s also often the best way to do business. Investors reap the rewards of powerful imitation on the part of companies that are themselves seen as innovators. Even the mighty Apple (NASDAQ:AAPL) knows a good idea when it sees it. Before the iPhone redefined the mobile device market, Nintendo (PINK:NTDOY) already had proven that touchscreen technology was desirable to consumers with its Nintendo DS portable gaming handheld. Nintendo in turn noted that people liked the sleek, simple design of Apple’s iPod and MacBook before making its Wii game console in the same mold.

Here is a look at who is copying who these days, and why a little mimicry might go a long way in bulking up business — or why it might tarnish a company’s reputation with consumers.

Google, Facebook and the New Gmail

Google (NASDAQ:GOOG) looks at Facebook and sees the lost opportunity of the century — a social network whose access to 800 million users will make it the leader in display advertising revenue by the end of the year. (Facebook is projected to pull in $2.19 billion in display revenue, while Google will take in $1.15 billion.)

It’s no wonder, then, that Google has spent recent years playing at being Facebook. The recently opened Google+ is in many ways a literal Facebook clone that incorporates Google’s other services like Gmail and Google Docs. Now, however, Google’s copying of Facebook is reaching into its other services. A Thursday report at Venture Beat said an accidentally published YouTube video showing off an upcoming redesign of Gmail showed that the email service looked somewhat familiar. As writer Tom Cheredar pointed out, the new layout — filled with white space, new organization tools that use images rather than text descriptors (a tiny trashcan instead of the word “trash,” etc.), and a stream of messages that look less like emails and more like conversations — is almost identical to Facebook’s messaging service.

On the surface, the switch is logical. Gmail has 260 million users, but 800 million Facebook users can’t be wrong. Google has to tread lightly, though, and not force Gmail users to adopt the new format — otherwise, it will have another Google Buzz on its hands.

Netflix, Amazon and Streaming Subscriptions

Netflix (NASDAQ:NFLX) might be having a tough time these days, but the problem has been with its public relations, not its product. People don’t like to pay more for things, but Netflix’s growth from 10 million users to more than 20 million users in just two years proved people sure do like streaming movies and television from the Internet to their TVs.

Amazon (NASDAQ:AMZN) has taken Netflix’s business model and is using it to transform itself into a service company in addition to being the Web’s biggest retailer. In January, Amazon began offering streaming video to Amazon Prime subscribers, positioning itself as a direct competitor to Netflix — but rumors suggest Amazon is going to apply the subscription model to more than just movies. In particular, Amazon is said to be preparing to offer a Netflix-style library of e-books, so Amazon Prime subscribers can access all the different entertainment they want on the new Kindle Fire tablet.

Offering many e-books for a blanket subscription rate is dangerous when individual e-book sales still are a growing business, but considering Wall Street analysts estimate that Amazon Prime is growing 20% year over year and total Amazon revenue grows 1.5% for every million Amazon Prime subscribers, the new model might yield far better results than plain ol’ electronic books.

Microsoft, Google and the New Windows

Microsoft (NASDAQ:MSFT) remembers the good old days, back when “Apple” was a word to be snickered at and “personal computer” was just shorthand for a device running Windows. The latter still holds true — Gartner, Inc. projects that the majority of PCs, 42%, will run Windows 7 by the end of 2011 — but the computer technology business ain’t what it used to be.

People are buying tablets and smartphones more than they’re buying PCs, and Windows is low on the mobile technology totem pole. Windows devices accounted for just 4% of the global smartphone market as of the second quarter, according to IDC. Windows 8, which made its debut in September, has been designed to follow Google’s Android model, an operating system that’s malleable enough to run on tablets and phones. Microsoft’s big hook, of course, is that Windows 8 also will run on PCs.

The company has a tough sell on its hands. Android phones makes up 52% of the global smartphone market, so manufacturers don’t have much incentive to switch to Windows. Early word on Windows 8 has been positive, though, so Microsoft’s all-device approach might work out yet.

As of this writing, Anthony John Agnello did not own a position in any of the stocks named here. Follow him on Twitter at @ajohnagnello and become a fan of InvestorPlace on Facebook.