It's my understanding (IANAL) that before formally entering the US (i.e. before passing *through* customs) that you have no rights. After all, you aren't in the US yet...

Now days folks who are concerned about their data, for whatever reason, can keep it "in the cloud" and access it via internet and wipe it from their hard drives before crossing borders. Google "cloud data backup" for lots of references. Sure, there can be security issues there, also, but it's generally out of the reach of customs.

I've heard of some companies *requiring* their employees who carry laptops to wipe their disks and carry no copies of information.

Kevin