The Obama Justice Department ought to look very carefully at the proposed merger of United Airlines and Continental Airlines. Together they would have more than a fifth of the U.S. market -- No. 1 in the country. Delta, which combined with Northwest Airlines in 2008, has 20 percent. So the top two carriers would control 41 percent of the market. Together they overlap on 13 non-stop routes, according to Bloomberg.

But the merger would have little effect on Marshall BWI, which is dominated by discount carrier Southwest Airlines. Continental has only a 3 percent share of BWI, and has a 5 percent piece.

In the end, don't expect the administration to contest the United-Continental combo. After all, these are the guys who allowed the egregious marriage of Ticketmaster and Live Nation. And where is the heralded Justice Department assault against Google?