The Consumerist's "Worst Company in America" award is based upon individual consumer votes.
Yes, there are "worse" companies than EA. But unless you live in the Gulf, BP did not directly affect you. While the big-name banks did ruin the economy, they did not directly empty out people's bank accounts. And Wal-Mart treats their employees like shit, consumers over look their practices because of the low prices.
IMO, EA was voted "worst" because they directly mistreat millions of customers. I, personally, was called "stupid at best, and a thief at worst" by the CEO of EA because SecuROM prevented me from playing the copy of Spore that I had purchased.
So, from the POV of a consumer, EA is the worst company in America because of how they directly treat millions of customers (who, for the most part, also happen to be online, where the polling took place).
Regardless, the company has been slapped with the label "Worst Company in America" two years in a row. And while it seems the company is making changes to try and address the image they have with consumers, I wouldn't hold out too much hope. Any real, positive changes would adversely affect their short-term bottom-line too much.