What's happening to our bees?

This story raises alarm about the status of pollinators so important to the fruit and vegetable industry. Apparently a mystery killer is causing the collapse of many commercial bee hives.
From The Philadelphia Inquirer:

"Every day, you hear of another operator," said Dennis vanEngelsdorp, acting state apiarist with the Pennsylvania Department of Agriculture. "It's just causing so much death so quickly that it's startling."At stake is the work the honeybees do, pollinating more than $15 billion worth of U.S. crops, including Pennsylvania's apple harvest, the fourth-largest in the nation, worth $45 million, and New Jersey's cranberries and blueberries. While a few crops, such as corn and wheat, are pollinated by the wind, most need bees. Without these insects, crop yields would fall dramatically. Agronomists estimate Americans owe one in three bites of food to bees.The problem caps 20 years of honeybee woes, including two mites that killed the valuable insect and a predatory beetle that attacked the honeycombs of weak or dead colonies.