Reuters has reported that the Department of Justice is taking a close look at the two-week ad alliance set up by Yahoo and Google because of antitrust implications. Part of the problem, according to sources, would seem to be a phone callthat Eric Schmidt, Google Chief Executive, supposedly made to Yahoo CEO Jerry Yang, offering to help stymie Microsoft’s takeover bid. Bothcompanies said they’d told all the relevant authorities about their two-week ad test, with Yahoo spokeswoman Tracy Schmaler saying, "Yahoo proactively kept the Department of Justiceinformed of its intentions to conduct this limited test with Google and have provided information to DOJ on the nature of the test." Although the ad test ends this week, reports are that theDepartment of Justice is worried about a longer-term deal.