The online world has sometimes been referred to as the Digital Wild West, a vast electronic prairie with few laws, where both good and bad actors carry on pretty much as they want. Like the Wild West, the new high-tech version can be a land of great opportunity — or great danger. Anyone or anything that has an online presence can be made a target, and that includes the U.S. Postal Service. Most people know the Postal Service has a website, www.usps.com, but it also has accounts on Twitter, Face