There's good news for all the entrepreneurial Davids struggling against overbearing Goliaths: the Justice Department has overturned a Bush-era policy on antitrust enforcement that made it easier for large companies to fight monopoly charges.

Christine Varney, the new assistant attorney general in charge of antitrust, rejected the previous administration's policy that concluded that most big companies make markets more efficient, and the Justice Department should only act if there's a big negative impact on consumers.

"Withdrawing the Section 2 report is a shift in philosophy and the clearest way to let everyone know that the Antitrust Division will be aggressively pursuing cases where monopolists try to use their dominance in the marketplace to stifle competition and harm consumers," she said.

The change is promising for small business fighting big competitors.

"The Justice Department ignored areas including monopolies and abuse of dominance, and this is very important to small businesses, medium-sized businesses, and even large companies that don't dominate a market," says Bert Foer, president of Washington advocacy group the American Antitrust Institute.

Even for small companies unable to afford expensive private lawsuits against monopolist competitors, the policy shift offers another option: Get the Justice Department to prosecute.