Conspiracy theorists will have a heyday with this one. A U.S. court of appeals has ruled that border guards have the right to inspect the hard drives of people entering the U.S., even if they don’t have any reason to be suspicious.
The case makes it so that all data on your hard drive is equally accessible. This is a continuation of the effects of an earlier Supreme Court ruling which essentially said that the fourth amendment (preventing unreasonable searches and seizures) does not apply at the border.
People who are really paranoid about their data will be looking for new ways to encrypt the contents of their machines, but this could present problems as well. Presumably, the border guards could lawfully ask to see the unencrypted data. Also, the presence of encrypted data could be perceived as reason for more suspicion and could cause even more problems for you. Still, I’m betting that people will find ways to get around the problem.