Man Becomes 'Accidental Millionaire' After Jet.com's Sale To Walmart (fortune.com)
The acquisition of Jet.com by Walmart for $3 billion in cash appears to have made the founder of IdeaDash an "accidental millionaire." Fortune reports: "Martin, who is the founder of a startup called IdeaDash, won Jet.com's nationwide marketing competition -- Jet Insider -- in early 2015. The contest offered a reward of 100,000 shares of Jet stock to the contestant who got the most people to sign up for 6-month free trial 'insider' memberships to the membership shopping site, a sort of online Costco or Sam's Club. According to his company's website, Martin took first place out of the 350,000 people who participated, getting over 8,000 people to sign up. Martin spent $18,000 on online ads, Bloomberg reports, and now has a stake in Jet that is reportedly worth millions. Although Martin told Bloomberg that he is not sure exactly what his stake is worth, Fusion reported in February 2015 that his piece could be valued between $10 million and $20 million."
He owns the same thing Walmart owns, though a smaller amount. Walmart thinks their portion is worth over $3 billion, so no the shares probably aren't worthless.
If the company is a) making money and b) not re-investing all of the profit go growth, they'll pay out the extra profit to shareholders as dividends. He'll get his portion of the dividends (profit).
If the company is growing quickly, and therefore reinvesting all profit, his holding increases in value as the company gets bigger, because eventually when it stops growing fast it'll be a bigger company paying bigger dividends.
If someone else wants those future dividends, they can get them by buying the stock from him today, in a private sale. Just because the stock isn't publicly traded doesn't mean it can't be privately traded.
The benefits of being publicly traded would just be that he wouldn't need to take the time to find a buyer, and he could more easily see how much the stock is selling for on any given day.