Defying the expression that no press is bad press, investors dumped shares of BP en masse on Wednesday, triggered by new estimates that the company's oil leak may be much larger than previously thought. The company's stock dropped more than 10 percent in one day, dipping to its lowest levels since 1996. Shares in the energy giant have lost half their value since the April 20 rig explosion that caused the spill, which will likely end up costing the company billions of dollars. Though BP claims to have "considerable firepower" to fund the clean-up efforts, others aren't so sure. BP is "in freefall," one energy analyst said. "There's an old saying: Don't try to catch a falling knife." Meanwhile in Washington, 30 lawmakers joined with President Obama to send BP Chief Tony Hayward a letter asking him to halt all dividend payments and advertising campaigns until the leak is stopped and spilled oil cleaned up.