An Apple founder, Ronald Wayne backed out early, selling his 10% stake for about $800. Today, that'd be worth about $43.8 billion.
Noah Glass, the Twitter co-founder no one remembers. He was forced out in 2006.
Frank "Reggie" Brown came up with the idea that became Snapchat, which is valued at $800 million. He's suing the co-founders for booting him in 2012.
Joe Jackson was asked to join the founding team at Facebook when Mark Zuckerberg first moved to Palo Alto, but turned it down to spend the summer interning for J.P. Morgan.
Ali Fedotowsky used up all of her vacation days at Facebook filming as a contestant on The Bachelor in 2010. When ABC asked her to be that year's Bachelorette, she quit her job and gave up her stock options to be on the show.
Sahil Lavingia was the second employee at Pinterest. He left the company just before his one year mark, so none of his stock options vested.
The Winklevoss twins collaborated with Mark Zuckerberg on a social network for Harvard students in 2003. In January 2004, Zuckerberg announced the "thefacebook.com." The brothers sued him for the theft of their idea and settled for millions, but not billions.
Dom Sagolla was head of quality at Odeo, the company that spawned Twitter. He was laid off in May 2006 and didn't receive any stock options.
Joe Green was one of Mark Zuckerberg's college roommates. After the pair got in trouble with Harvard over their Face Mash application, his father told him not to work with Zuckerberg.
Alex Macgillivray used to be Twitter's general counsel. He left that role in August, and his shares weren't mentioned in the IPO filing.
Alberto Savoia left his engineering director role at Google where he had led the team that created AdWords. He left two years before its IPO to found a software testing company.
Florian Weber was one of the first engineers hired to work on Twitter. Unfortunately, he was hired as a contractor and not an employee, meaning he received no stock options.
Kevin Systrom had a number of chances to make millions before his success at Instagram. He turned down a job offer at pre-IPO Facebook. He interned at the company that became Twitter. The eventual purchase of Instagram for $1 billion made up for these missed opportunities.
Everyone loves a Silicon Valley success story: A handful of smart, driven young entrepreneurs gets together to work on a passion project, find an idea with real legs, and are rewarded with an lucrative "exit" of making it big or being purchased by one of the industry's giants.
While there are notable examples of software company exits making thousands of people wealthy, there are always cases of workers who for one reason or another miss out on their potential fortunes.
Some leave for other opportunities that they are more passionate about. Others leave to found their own companies. Some just made decisions they regret.