This morning Volkswagen (VOW) was worth more than Exxon Mobile (XOM) as common shares rocketed up as much as 93% on a short squeeze.

Prosche, in an attempt to take over the carmaker has engineered a shortage of common shares by gobbling up as much as 75% of the company via options. The counter parties to these options went long the actual stock to hedge their exposure, leaving the shorts scrambling for shares to buy back.

Volkswagen Overtakes Exxon as Most Valuable Company (Update1): “Volkswagen AG became the world's biggest company by market value after Porsche SE announced plans to raise its stake in the German carmaker to 75 percent, triggering demand from short-sellers.

Volkswagen rose as much as 485.01 euros, or 93 percent, to 1,005.01 euros and was up 55 percent as of 11:10 a.m. in Frankfurt trading. Wolfsburg, Germany-based Volkswagen has risen more than fivefold this year and at its intraday peak was valued at 296 billion euros ($370 billion), more than Exxon Mobil Corp.'s $343 billion market value at yesterday's closing price in New York, according to data compiled by Bloomberg.

Porsche, the maker of the 911 sports car, has accumulated Volkswagen shares since 2005 in an effort to protect ties to its largest supplier. Porsche said Oct. 26 that it aims to increase its holding from 42.6 percent. That prompted some short-sellers to buy from a shrinking pool of stock to end their bets. BaFin, Germany's financial-market regulator, said today that it's monitoring trading in Volkswagen shares following the gains.

“One of the biggest risks with the herd mentality approach to shorting is that a lot of money can be made on the outset,” said Ed Oliver, a senior business consultant at Spitalfields Advisors, a London-based firm specializing in securities lending.