If someone steals my chromebook while it's off, will him be able to see my cached data?
Solution 1:
I used Google to find this.
Data Encryption - When using web apps on a Chromebook, all important data is stored safely in the cloud. Certain kinds of files, like downloads, cookies, and browser cache files, may still be present on the computer. The Chromebook encrypts this data using tamper-resistant hardware, making it very difficult for anyone to access those files.
There's a very detailed description of the encryption mechanism for cached data here.