In my opinion, everyone has the capacity to become a millionaire but most people do not have the drive, determination, or are unwilling to make the sacrifices to become a millionaire.
Milton Snavely Hershey founded 4 companies and declared bankruptcy before he became successful with the Hershey Chocolate Company that he founded when he was 43 years old.
Many of the successful people I know in real life did not find success early (like the Facebook guys), the built several companies that were less than successful, and learned from their mistakes, and when they were in their 40s or 50s they seemed to have the Midas touch because they really understood what they were doing.
Today it is easier to start your own business, and it is possible to fail without losing much money. For example, creating a web application (like this site), building an iPhone app, or even games for XBox Live Arcade is easy to do without spending much money at all; and regardless of whether you succeed or fail you will have learned something useful to your next attempt at starting a company.
