Insecure OS X
A well-known security hole in later versions of Apple OSX allows users to boot into recovery mode and reset the admin or root password. Sure, this is great if you forget your password, but this also means that any would-be hacker can get into you Mac with little to no problem. Now there are things you can do to protect yourself without having to switch to Linux or Windows, like hard drive encryption. Not that Windows or Linux are perfectly secure. Far from it! Here is a video that demonstrates how it is done.
FileVault comes with Mac OS X and you can read an article about how to turn it on here.
For a list of other Disk encryption software that will run on Mac OS X you can check out the page “Comparison of disk encryption software” on Wikipedia
I must give the disclaimer that it is against the law to access a computer you do not have permission to access.
Thanks to student Tim D. for the information.