a federal appeals court has ruled on the legality of such searches. The result: Yeah, customs can do whatever it wants to your computer when you come across the border, without a warrant, and without cause.
The ruling extends to all electronics: In addition to laptops, feds can seize phone records and even digital pictures on your camera as they hunt for evidence. The ruling was unanimous among the three appellate judges.
http://tech.yahoo.com/blogs/null/90325I'm sure they're not liable for sporking up the entire computer in the process either. "Oh we're sorry we ruined your company presentation Mr. Citizen, despite the fact that you worked 4 months on it, despite the fact that it's critical to your business meeting in London, and we've probably destroyed your career in the process. Oh yeah, and those were lovely pictures of your wife, terribly sorry for accidentally deleting them. We're just looking out for you, after all." I really hope this gets a 4th Amendment challenge at the Supreme Court and gets overturned.
To any foreigners planning on coming into the US, you might want to consider backing up everything and getting an insurance policy on your equipment before bringing it along, and make sure it covers damage from customs goons. I'm dead serious, they will break your stuff and good luck on getting anything back.
Edit: One other thing I might mention. The Feds can use child pornography as a convenient excuse to prosecute at will. Consider this hypothetical situation. Say you live in another country where the legal age for adult material is less than the legal age for adult material in the United States. You then enter the United States with photographs of an individual under the US legal age. Guess what happens...? Remember, to the law, a child doesn't mean a "cute little kid", it means anyone under a specific age in the US, I believe 18. I don't know what the laws are in other countries but I've seen the Feds crucify people over this sort of technicality for no other reason than the fact that they can, despite the fact that in a person's home country they would not have broken any law. Just something to keep in mind.