Initial Public Offerings (IPO) get a lot of media attention for various reasons; most offerings swoon in the coming weeks, some (famously) like Facebook. Others zoom (like Google), but often come back to earth eventually. IPO fever is one way of looking at overexcited markets. Many companies remain private and never have (or want to have) public ownership. Going public means much more scrutiny, legal entanglements, and lowers freedom of action. The best reason(s) for going through an IPO is (are):

		To cash out options given to insiders, including early employees.
		Publicity for the product of your company and the publication of your Market Cap.
		It helps investment banks earn large fees for underwriting the offering.
		Increased liquidity for shareholders and access to public funds for company development.