As Mark Twain may or may not have said, "History doesn't repeat itself, but it does rhyme."

We here at The Fool believe some historical perspective can go a long way to help investors successfully navigate the market's inevitable ups and downs. So as tech investors everywhere scour the market for fresh opportunities with the start of the new year, let's briefly review the tech trends, and one stock associated with each, that dominated the news in 2015.

1. Mobile growth is slowing
The rise of smartphones and the explosion in mobile computing has been one of the most important tech trends in recent years, and a very profitable one for many investors. However, while 2015 saw continued smartphone sales growth, this once-hot market logged its slowest year of growth on record. Though it hasn't published the final tally, research firm IDC predicted that global smartphone growth would slow to 10.4% in 2015, down from 27.5% the year prior. Of course, with an estimated 1.4 billion units expected to have been shipped last year, slowing growth doesn't mean there's no money to be made for investors as mobile computing grows into a mature marketplace.

Company at the heart of it all: Apple (NASDAQ:AAPL)
Apple's selection should be no surprise, as the world's largest publicly traded company once again set records for virtually every financial metric in 2015, largely powered by its most important product -- the iPhone. As is customary in each odd-numbered year, Apple refreshed its iPhone's form factor in 2015, and again it did so to record results. Apple sold over 231 million iPhones during its fiscal 2015, which ends in October. And though Apple's iOS accounts for just an estimated 15.6% of the global smartphone market, the company has long been believed to capture the vast majority of the industry's profits.Yet despite all its recent successes, Apple's shares are effectively flat over the past 12 months, and its price-to-earnings ratio of 11 makes it a downright steal compared to the S&P 500's 21.

2. Social-media stocks are on the rise
Social networks the world over continued to redefine the media landscape, and even as many of the companies that now dominate the industry move toward maturity, they're still building massive businesses atop their sizable user bases. According to researcher eMarketer, worldwide ad spending on social networks was set to rise 33.5% in 2015, which is just part of the broader growth story currently unfolding in this space. From 2013 to 2017, social-media ad sales are expected to increase from $11 billion to nearly $36 billion.

Source: Facebook.

Company at the heart of it all: Facebook (NASDAQ:FB)
No other company dominates the social-media landscape quite like Facebook. Its unmatched combination of user detail and massive scale give it one of the most impressive growth opportunities anywhere in tech. Through the first nine months of 2015, Facebook's revenue increased an impressive 50% to a whopping $12 billion.

Beyond its core business, Facebook also enjoys ample ancillary growth opportunities thanks to its savvy acquisition strategy. Though at varying stages of their business evolutions, Facebook subsidiaries Instagram, WhatsApp, and Oculus VR all appear to enjoy multibillion-dollar business opportunities in their own right. So while Facebook stock is by no means cheap, there are plenty of reasons to like Facebook shares in 2016 and beyond.

3. Cloud computing continues to surge
Though the term "cloud computing" encompasses an increasingly diverse series of sub-segments, "growth" is one word that defines the entire space. According to Forrester research, global cloud-computing spending rose an impressive 21% in 2015. What's more, cloud-computing spending appears poised to top $100 billion for the first time ever in 2016. Yet despite its size, the competition for leadership in this gargantuan market is becoming concentrated among a handful of well-established industry names.


Company at the heart of it all: (NASDAQ:AMZN)
As one of the best-performing stocks of 2015, Amazon appears downright expensive. However, with the company's direct exposure to two of technology's largest revolutions, investors may be underappreciating the sheer extent of Amazon's potential growth opportunities. Thanks to its ongoing investments in fulfillment and delivery infrastructure and strong bargaining power, Amazon remains the odds-on bet to dominate e-commerce well into the future. Moreover, Amazon controls an estimated 30%of the global cloud computing market, and Amazon Web Services' surprising profitability should provide a crucial profit center to support the long-term investments in its low-margin retail business.