Department of Justice antitrust investigators may just as well start leasing space at Google's Mountain View, CA headquarters. The Wall Street Journal reports that the search giant is pondering a bid for Yahoo, reaching out to a pair of private equity firms about assisting with financing.

Google obviously doesn't need help in search, but Yahoo has put itself up for sale and the company brings some things to the table that Google would find useful. First and foremost is an audience of around 700 million unique visitors every month that could theoretically become users of Google+ and other services. The Journal's usual "people familiar with the matter" also say that Google would love to extend its advertising reach across Yahoo.

If the report is accurate, there is one massive hurdle facing any attempt by Google to buy Yahoo—antitrust. Back in 2008, the two 'Net titans inked an ad-test pact. Three percent of Yahoo searches would have been given Google results, with the possibility of that percentage increasing, depending on performance. Of course, not only did the percentage not increase, but the deal never went down. The US Department of Justice quickly began investigating the transaction, as did EU regulators. Those antitrust concerns ultimately scuttled the deal, and it's not clear why Google believes the outcome would be any different this time around. Google's share of both the search and online advertising market have done nothing but grow since the last time it dallied with Yahoo, so the antitrust scrutiny would be even greater.

There may be method to Google's madness, however. Reports emerged a couple of weeks ago that Microsoft was contemplating another bid for Yahoo, and Google may be trying to get Microsoft into a bidding war. Remember: Redmond famously made a massive bid for Yahoo in early 2008, one that Yahoo wasn't terribly interested in. Microsoft spent a few months trying to convince Yahoo's leadership that an acquisition was in the company's best interests, but eventually gave up, a decision Microsoft CEO Steve Ballmer believes was the right one in retrospect. The two companies did a search partnership that made Bing the default search engine for Yahoo.

We don't think a Microsoft acquisition of Yahoo makes sense in the current market. Although Yahoo's margins are up, sales are shrinking, its core business is ailing, and much of its talent has left. There's not a lot of value there for Microsoft. And although Google would love to get Yahoo's 700 million visitors using Google services, it's difficult to imagine antitrust regulators approving an acquisition.