Running a business is a huge gamble, and it takes a certian kind of personality to become one. Not all entrepreneurs would go to the same lengths as the founder of FedEx, but the amount of riskes they take everyday are staggering. They often risk losing everything at multiple points in their career.
Yes, entrepreneurs are gamblers by nature. They invest their money into ideas that they believe are good ones but they do not know will be successful. Their idea may be one of the best new ideas and make them rich or it could flop and they can lose a lot of money. Thus, entrepreneurs must be willing to take risks.
Succeeding as an entrepreneur has always required a tolerance for risk, reflected in the motto "no risk, no reward." Gambling in Vegas is the extreme of that attitude. When deciding to become an entrepreneur, one agrees to forgo financial security in the short run, hoping for financial security in the long run.
No, entrepreneurs are not gamblers by nature. The actions of the founder of FedEx show a stroke of luck, not solid business sense. When entrepreneurs gamble with their company and their investors' money, they are committing an unethical act. Strong entrepreneurs seek to strengthen their business to succeed versus gamble its future.