This article on the StarCite service in Philly.com proves that plenty of business opportunities exist in existing markets. The service of meeting planning has probably been around since the advent of economies of scale. As the article states,
In this country alone, industry experts estimate that 800 million people a year attend business meetings of 10 or more, evidence that people still need face-to-face contact in the digital age
thus defines an established market with many solutions and many providers.
What did StarCite do that made them stand out from the crowd? They put information in customer hands by increasing transparency, they made it simple and they made their software available 24 hours, seven days a week. By doing so, they created happy customers. Customers who refer additional business and create sustainable growth.
You may think you have a idea for a great new product or service but do you know who the customers will be? Would your time, effort and money be better spent finding dissatisfied customers in an existing market and helping them? I would encourage you to spend two weeks noting all of the services or products you wished were better and taking a hard look at starting a small business around one of those ideas.