Nasdaq is launching what its executives are calling one of the most significant developments on Wall Street in decades a private stock market for super-wealthy investors. Minimum requirement for traders: $100 million in assets. Any private firm can list on Nasdaq's new platform, which is called the Portal Market, and raise money by selling stock to an elite group of shareholders. These companies would remain private and not have to make public their financial statements or submit to federal regulation, such as the Sarbanes-Oxley corporate accountability law. Analysts say the new ease-of-use is another incentive for super-wealthy investing groups to shun the public markets and focus on making money in the private sphere.