A recent 51-page Privacy Impact Assessment supports the right of U.S. Immigration and Customs Enforcement agents to copy, download, retain or seize any content from laptops, cellphones or other electronic devices. Without giving any reason for the search or seizure. Read It.
Last months DHS Privacy Office report to Congress states that more than 144 million travelers were processed at US ports of entry between Oct 1st 2008 and May 5th 2009. Read It. Of those 1,947 electronic media searches took place. Of those 696 searches were of laptops. This could have been something as simple as turing on the unit to confirm it was indeed a working laptop and not a fake. Of those the officers conducted in-depth searches of 40 laptops. No description of what an in-depth search is, or how long they retained the equipment.
It should be noted that your equipment can currently be held for a maximum of 30 days. Officers must consult agency lawyers if they want to view a journalist's work-related data or a traveler's sensitive legal material or medical records.