Recent and not so recent laws allowed US customs to search trough peoples' laptops. This search includes copying and reading all your data, and sometimes getting the laptop (or it's parts) takes days or even weeks. It is only a question of time before other countries allow the same.
Technology news - CNET News.com delivers
an article that explains how you can defend yourself and your sensitive data from things like this. The tips found there are also a great thing to protect your data from possible theft!
The implications on this can be really severe as journalists might keep notes on confidential sources, or sensitive business documents can be stored in a computer. If we managed to make you worried take a look at the
full article.