But in the case of a border crossing, the cloud actually becomes a safer place, provided your laptop or cell phone doesn’t have access to it. As long as there’s no nexus between your device and the cloud, you aren’t crossing the border with that cloud data, so it’s not subject to search.
The travel-only Gmail account: A practical proposal for digital privacy at the US border
Ken Kinder

Only if you use an encrypted cloud service like Spideroak, because under the PATRIOT Act’s lower legal standard it’s easier for federal agents to get warrants to search cloud services for your data. Using Spideroak would likely render such a warrant useless.