As a Linux geek ... I must correct this. The information High Seas posts is simply wrong on almost any Linux system (unless it is set up in a really absurd way).
Linux has user permissions for exactly this reason. System files are not deletable by users without specifically requesting extra permission. This permission is only obtainable by password which must be provided by the adminstrator.
Most files you can delete will be files that you created yourself.
Modern distributions of Linux (e.g. Ubuntu) are very picky about user permissions. They set up the system with a conservative user policy. This can be changed... but you have to know what you are doing (and anyone who knows how to do this will also know how to use "rm").
Yes, the advice about the 'rm -i' command is good.
But the impression that the Linux OS is easy to "delete" with one command is completely bogus.
The user permission scheme on Linux makes it safer than Windows XP to the point that Window Vista (the newest version of Windows) tries to implement a similar one.