Bad Idea
 

I'm starting to get the hang of the linux command line and I have a question. First know that of course I am not going to be dum enough to try this but, if I executed these commands:

#chgrp --recursive marcus /
#chown --recursive marcus /

Would that give me permission to open up any folder anywhere on the hard drive and delete it without root permission and without being prompted for the root password or anything?

It might, but then anything installed that depended on being owned by 'root' would break. So... if you wanted to really scrogg a system, it might be an educational experiment.... ;)