Wouldn’t it be great to have a crystal ball? Some way to see into the future and learn if you just made a genius decision or a big mistake?
The folks on this list sure could have used that.
The tech industry is filled with stories of people striking it rich.
Atari founder Nolan Bushnell turned down the opportunity to invest $50,000 in seed money in Apple. At Atari, Bushnell was one of Steve Jobs' first bosses.
Had Bushnell said yes, he would have owned a third of Apple, a company that is today valued at about $480 billion.
Ronald Wayne, Apple's third co-founder, sold his 10% stake in Apple for $US800 two weeks after launch. He later got $US1,500 for renouncing all claims to ownership.
If he had kept it, it would be worth about $US40 billion today.
Back in the 1970s Steve Wozniak worked for Hewlett-Packard designing engineering calculators. In his spare time, he created a PC that would later become the Apple 1 computer.
Five times, Woz begged the executives at HP, led by then-CEO John Young, to manufacture his PC. They said no. So he left HP to start a company called Apple with his buddy Steve Jobs.
Mark Zuckerberg's college roommate, Joe Green, turned down an offer to help Zuckerberg start Facebook.
When the two were at Harvard, they created a Hot-or-Not style website called Facemash, which got the pair in trouble with the university. When Zuck asked Green to help him with Facebook, Green's dad discouraged his son from doing another project with Zuck.
Had Green joined the company in those early days, he would have gotten about about a 5% stake, he thinks, which today would be worth about $US7 billion.
Facebook got its start in Zuckerberg's Harvard dorm room. And it might have stayed in the Boston area if Battery Ventures, a venture-capital firm based there, hadn't walked away from negotiations with Zuckerberg back in 2004.
Battery Ventures partner Scott Tobin, who was involved in that meeting, later called Facebook 'the biggest fish that ever got away.'
Stuart Ellman, co-founder and managing partner at New York venture firm RRE Ventures, met Mark Zuckerberg by phone when Zuck was still working from his Harvard dorm room.
Ellman took the call through an introduction from Zuckerberg's classmate Sam Lessin, who was a summer analyst at RRE, but didn't get the chance to invest, he revealed at a Business Insider conference.
A few years ago, tech investor Bessemer Venture Partners published what it called its 'anti-portfolio.' That's a list of companies it could have invested in, but didn't. It was an entertaining look at the VC world.
One of the best stories is how partner David Cowan missed his chance to seed Google. Cowan's college friend, Susan Wojcicki, had rented her garage to Sergey Brin and Larry Page as the first office for Google. She tried to get Cowan to meet with them.
Instead, Cowan painstakingly avoided the garage and the two co-founders at work there.
James Altucher is another venture capitalist who passed on funding Google, calling it 'the worst venture capital decision in history, he explains in his blog:
Back around 2000, a junior partner told Altucher that they could buy 20% of Google for about $US1 million, and Altucher replied: 'Search engines? Aren't they all dead? What's the stock price on Excite these days? You know what it is? Zero!' (Excite was in the process of going bankrupt.)
So Altucher's partner told Google, no thanks, saying, 'The opportunity is too small for us.'
In 2012, Brett O'Brien's startup Viddy was a sensation. Photo-sharing app Instagram had just been acquired by Facebook for $US1 billion, and Viddy -- often called the 'Instagram for video' -- had about 30 million monthly users.
Twitter reportedly came looking to buy the company for somewhere in the $US100 million range, but Viddy walked. (O'Brien denies those reports, saying the Twitter talks didn't progress into an actual offer.)
Too bad O'Brien didn't get Twitter to make an offer. Viddy's popularity has since taken a nosedive, O'Brien lost his job as CEO and the company gave back $US18 million to its investors.
RIM co-founder Mike Lazaridis was once the king of the mobile world.
Then came 2008, when BlackBerry -- then known as Research In Motion -- entered into a nose dive from which it has yet to recover. In those days, its users were fanatically loyal and waiting for the touchscreen BlackBerry Storm to counter the iPhone.
But the Storm was buggy and hard to use, sending them into Apple's arms.
Lazaridis stepped down as co-CEO in late 2011, left BlackBerry's board of directors in 2013. It's market cap is now under $US5 billion, a fraction of the over $US83 billion it enjoyed back its heyday.
Yahoo CEO Jerry Yang infamously turned down a $US31-a-share, $US44.6 billion offer from Microsoft in 2009.
Many shareholders were unhappy and wanted Yahoo to sell. All the drama sent the company into a downward spiral for years. Now that former Google executive Marissa Mayer in charge, Yahoo is finally on the mend.
Still, who knows what the search engine market would look like today if the No. 2 and No. 3 search providers had combined in 2009?
Andrew Mason turned down a $US6 billion buyout offer from Google. Instead, he opted to take Groupon public.
The IPO raised $US700 million, and the company was briefly valued at more than $US12 billion.
But the stock promptly tanked after Groupon missed earnings forecasts and struggled with its accounting and in 2013, Mason was fired. Today shares are trading under $US8 and the company has a market cap of about $US5 billion.
Sahil Lavingia was the second employee at Pinterest, hired on as a teenager, and leaving before the site took off.
His timing could have been better. Lavingia left Pinterest about one month shy of being there for a full year so none of his stock options vested.
But he's got no regrets. At 19, he became CEO of Gumroad, a startup that generated a lot of buzz in 2012 and landed $US8 million in venture funding almost immediately.
Hopefully he'll make it with Gumroad. Meanwhile, Pinterest's valuation has recently been pegged at about $US4 billion.
Enterprise cloud company Box has raised over $US400 million from investors at a $US2 billion valuation and is about to go public.
Mark Cuban should have owned a big chunk of that. He famously backed Box with a $US350,000 seed investment after Aaron Levie, then a college student, emailed him a pitch. But Cuban didn't agree with Levie's business model and about a year into the company, Levie raised an investment to buy Cuban out.
Cuban, who is worth an estimated $US2.5 billion isn't crying over it. He still tweeting that he doesn't like Box's businss model.