My guess would be they cannot pass the higher listing standards of the NASDAQor the NYSE. To be a legitimate public company they have to be listed where the shares canbe traded. If not tradable they would never be able to execute an IPO andtherefore could never raise the capital to be an ongoing concern. Companies usually begin by seeking private equity either that raised fromventure capital firms or individuals. When the money begins to run out theymade not be able to continue to afford their payroll and other expenses. Theyare always trading partial ownership in their company to continue as anongoing concern. When private equity runs out they turn to the public marketsthrough an IPO but to be listed they need to have a history of sufficientequity revenues or profits. When they cannot meet those requirements theyopt for the listings you named until they meet those more stringentrequirements. Otherwise they run out of money.