If you're crossing a border into the United States, the government can take away anything electronic for any reason for any length of time and give the information on it to others.
Read more here.
Many scientists cross American borders to go to conferences or to do field work. And most are highly dependent on their laptops in particular, which are often used for data collection, grant writing, and so on. Taking away a computer could be devastating. So I'm labeling this one as "Science and politics."