A challenge for today's CEOs is competition from an emerging rival and evolving economics of the business. It used to be that there was a dominate business model in one industry for decades with companies focusing on better implementation or better quality. But industry experts note that in the last twenty years a lot of business models and brands have been expiring. CEOs must think about how their companies will generate revenue and offer value to customers. Innovation, new products and services offer the greatest opportunity for growth for their companies. But in order to survive for decades to come, many CEOs are coming to the realization that they must reinvent their business models. There are several iconic brands on the verge of dying, according to the HuffingtonPost.com. And if they don't reshape their business models, these big brand names may be out of business for good. Here's six that are in trouble: 1. Quiznos. Founded in 1981, Quiznos' sandwiches were set apart from others in that they toasted each and every one. But once every other sandwich chain started toasting their sandwiches, Quiznos just wasn't that unique anymore. Moreover, Quiznos kept its prices well above Subway's, which likely cost them with customers during the recession, reports the HuffingtonPost. Quiznos has gone down from 5,000 stores to around 2,100 with hundreds of more locations closing. The Denver-based chain also is in heavy debt to the tune of $600 million. In contrast, Subway is one of the world's most profitable brands. 2. Red Lobster. Still one of the biggest American casual dining restaurants dedicated to seafood–and Cheddar Biscuits, Red Lobster as with many sit-down restaurant chains has been doing poorly lately. The economy has given birth to a variety of new and different fast-casual dining establishments. Many of these restaurants don't require waiter service such as Panera Bread and Smashburger. In December 2013, parent company Darden Restaurants announced that it had intentions to sell Red Lobster or spin it off into its own company, setting off social media frenzy that the restaurant had gone out of business. Red Lobster's other problem is that the shellfish isn't so special anymore now that diners can get cheap lobster meals as places like Golden Corral and Whole Foods, reports the Wall Street Journal. 3. BlackBerry. Right before the iPhone was announced, BlackBerry phones were the most popular mobile devices on the market. iPhones helped popularize Google's Android operating system. The revolutionary touchscreen smartphone turned the Blackberry into an antiquated device. BlackBerry was mistaken to think that their phone with a keyboard would still attract more professional and business-oriented people. Regardless of whether they used their phone for business or pleasure, many people switched over to the iPhone. Even BlackBerry's latest device–a touchscreen smartphone released in January 2013 – failed to take off. To the contrary, Samsung, the creators of the popular Galaxy smartphone have risen to the top of the mobile game, besting Apple's as the most profitable smartphone company, according to the Global Brand Simplicity Index 2013. RELATED: Say Goodbye to Your Twinkies and Wonderbread 4. Zynga. Founded in 2007, the gaming company was worth around $20 billion at one point, having launched one of the most popular social networking games ever: FarmVille. In the past couple of years, the company has been plagued by bad investments and employee complaints about workplace standards. Moreover, Zynga relied too heavily on Facebook, and as the social network changed, the company couldn't keep up, the HuffingtonPost reports. The company has hired a new CEO, Don Mattrick, the former head of Microsoft's Xbox, who is challenged with thinking of a way to successfully transition Zynga's online gaming platforms onto a mobile setting. 5. Volvo. Volvo, long ago considered a safe and approachable vehicle, competes with way too many car brands. The Swedish manufacturer is in direct competition with mid-luxury cars, like Toyota and General Motors, while also finding itself up against lower-priced high-end cars from Mercedes and BMW, reports the HuffingtonPost. Therefore, the demand for Volvo, which offers a small selection of cars, has suffered. In comparison, Volkswagen owns Audi, Porsche, Skoda and Seat car brands, allowing for a company with a more diverse and broader audience since they can market their cars to people of all financial levels. 6. Martha Stewart Living. Lifestyle personality Martha Stewart is extremely popular, so it only makes sense that her magazine and television show, both of which started in the early 1990's, would resonate very well with the American public. Martha Stewart Living magazine can't sell any advertising pages. Publishing revenue dropped to $19.4 million, from $27.6 million between 2012 and 2013. The company laid off 100 workers in December 2013 and in restructuring the publishing division, two of its smaller magazines were discontinued: Everyday Food and Whole Living. Martha Stewart Living Omnimedia is undergoing a huge restructuring from a media company to a merchandising enterprise. RELATED: Radio Shack, JC Penney and Others Closing Their Doors