Being root on a system opens you up to a lot of catastrophes, such as accidently issuing a rm -rf command, wiping your system completely clean. The reason MS Windows has problems with Virii is lack of user security. Anything and everything can be executed, and run from your account.
Root can execute any commands on the system that can damage your system. Someone could create a shell script which can force installation of trojan apps onto your system. If you were a user, then running such a script would limit the shell script from installing potentially damaging software.
With GNU/Linux, you can create many user accounts, and use su to temporarily become root, for installing packages, or better, use sudo to run installation programs.
What makes *NIX such a stable system is the file permissions, user permissions, by being root full-time you are loosing this extra security.
There is no reason you should be using your system under a root account. If you do not know how to make a user, ask that question.