Actually, I don't believe the stated reason, that "birth certificates and other forms are government ID are prohibited on eBay", is their real reason. After all, eBay has had no qualms at all about allowing auctions of valid stolen Albuquerque Police Department ID, badges, and similar items government ID as referenced in their stated reason despite formal complaints by the City of Albuquerque and formal requests that those auctions be cancelled.
Now I'm just waiting to see what happens next.
UPDATE: It appears the U.S. Army also believes the eBay birth certificate could be real. At least that's one message the Pentagon is giving. The Pentagon has cancelled the orders of Army Reserve Major Stefan Cook. Cook had sued to get his orders cancelled on the grounds that Obama is not eligible to be president, and order such deployments, because he was not born in the United States. By cancelling Cook's orders, the Pentagon admits he might be right.