Oprah Winfrey's investment in Weight Watchers (NYSE:WTW) reportedly netted her a one-day paper gain of $70 million after the weight-loss center's stock soared on the news she took a 10% stake in the company and a seat on its board of directors. But the half-billion-dollar gain in Weight Watchers' market cap due to the "Oprah effect" remains a risky bet that the heavily indebted, customer-losing company can turn itself around.

Photo: aphrodite-in-nyc.

Taking fliers on risky investments seems to be a hallmark of celebrity investors. Actors Sylvester Stallone, Bruce Willis, and Arnold Schwarzenegger invested in the Planet Hollywood chain that, at one time, had almost 100 restaurants open; but after several bankruptcies, it's left with just six.

Ice skater Dorothy Hamill invested in the Ice Capades, which, like Oprah's Weight Watchers deal, also seemed like a natural fit, but it went bankrupt and subsequently sent her seeking the protection of the courts, too.

Even when stars do have big successes, like U2 frontman Bono, whose venture capital firm Elevation Partners were early investors in both Yelp and Facebook, they can still suffer big losses. Elevation had previously invested in magazine publisher Forbes Media and mobile device pioneer Palm, but both investments ended up needing to be rescued -- by an Asian investment firm in the case of Forbes, and by Hewlett-Packard's buyout of Palm.

Still, celebrities do seem to have their fill of successes beyond the likes of Ashton Kutchner, who is almost synonymous with small-tech start-ups, and who invested in Skype just two years before it was bought out by Microsoft. Below are four additional entertainment industry A-listers who have seen their investments pay off big.

50 Cent and Vitaminwater 
Having survived being shot nine times, Curtis "50 Cent" Jackson went on to become one of the hottest hip-hop artists with his album Get Rich or Die Tryin. His manager hooked Jackson up with a Reebok commercial, and knowing the advertising executive for Glaceau would see it, he had the rapper take a big swig of the water company's Vitaminwater at the end.

Curtis "50 Cent" Jackson turned water into gold with his investment in Vitaminwater. Photo: Disney|ABC Television Group.

The manager's hunch was right, and the executive quickly inked a deal with Jackson that saw the hip-hop star get a reputed 10% stake in the company. A few years later, Coca-Cola bought Glaceau for $4.1 billion, and 50 Cent was suddenly worth a lot more than that, netting an estimated $60 million to $100 million from the deal.

Dr. Dre and Beats
Also coming from the rap scene, Dr. Dre had become something of a hip-hop impresario since his days with the hardcore rap group N.W.A, which was just recently profiled in the movie Straight Outta Compton. By 2008, he was an industry powerbroker, and together with Monster Products and legendary record producer Jimmy Iovine, Dre created Beats high-performance headphones. It subsequently expanded into streaming music, which caught the eye of Apple, and $3.2 billion later, Dr. Dre further cemented his position as the richest man in rap.

Dr. Dre is a long way from the streets of Compton after the deal with Apple for Beats was completed. Photo: foeoc kannilc.

Madonna and Vita Coco
The Like a Virgin singer Madonna was said to like the taste of virgin coconut water so much that, in 2010, she invested $1.5 million in the leading producer of the rehydrating beverage Vita Coco, which had a 60% share of the market. Since then, rival Coca-Cola took a minority stake in Zico reportedly for "way less" than what it paid for Vitaminwater, and PepsiCo introduced its own O.N.E. brand.

People may have thoughts Madonna was nuts for investing in coconut water maker Vita Coco, but she was literally putting her money where her mouth was. Photo: David Shankbone.

Vita Coco was largely controlled by its two co-founders and a Belgian investment firm tied to Anheuser-Busch InBev, who held equal shares totalling about 80% of the company. Last year, however, Vita Coco sold a 25% stake in the business to Reignwood Group, the parent company of Red Bull China, at an enterprise valuation of U.S. $665 million.

William Shatner and Priceline.com.
These days, William Shatner may be just as famous for his portrayal of priceline.com's (NASDAQ:PCLN) The Negotiator as being Captain Kirk from Star Trek -- so much so that the online travel agency was forced to bring him back after killing him off in one commercial. Yet when he first signed on for the role, he asked to be paid in stock options in the company rather than cash, and at one point, was said to have made as much as $600 million as a result, at least on paper. But like others who were hit by the tech wreck of 2000, Shatner sold his stock and realized a much lower profit.

Image: Priceline.com

Perhaps Shatner's gains shouldn't be looked upon as a "successful investment." While lots of investors were shaken out of the market during its crash, between January 2000 and today, Priceline's stock has quintupled in value, and was recently trading near all-time highs of almost $1,400 a share. That's a lot of money left on the table.

Rich Duprey has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Apple, Facebook, PepsiCo, and Priceline Group. The Motley Fool owns shares of Microsoft and has the following options: long January 2016 $37 calls on Coca-Cola, short January 2016 $43 calls on Coca-Cola, and short January 2016 $37 puts on Coca-Cola. The Motley Fool recommends Coca-Cola and Yelp. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.