There is no requirement that the owners of electronic equipment be suspected of any crime or any other form of wrongdoing. Homeland Security will take your computer at will, without explanation, just because it wants to, and you might never get it back.
Once you accept the truth of what Secretary Chertoff is saying, it becomes plain that terrorists are flooding across the borders into the United States every day. The new generations of terrorists look like non-terrorists, see. They have legitimate passports, and they’ve never committed any act of terrorism, or even been caught associating with terrorists. That’s how you know they’re terrorists.