Apple has a press release out this morning trumpeting the iPad reaching the million units sold milestone after only 28 days on the market, but it might want to cool it on the boasting for a while. According to a report in the NY Post this morning, citing “a person familiar with the matter,” regulators at the FTC and the Department of Justice are in the final stages of negotiations over which agency will lead an antitrust investigation into Apple’s policy of requiring iPhone and iPad app developers to use only Apple-approved development tools. One of the issues in any such investigation is whether a company has “market power” within the meaning of antitrust law. Does Apple have market power in the apps market? We may soon find out.