OK just to clear things up here... Android is not Windows, it is Linux. The only way you can mess with a Linux Kernel is if you have root access. This will allow you to access the file system. (not like a Windows folder where anyone can write over the system files)
Everyone who has an Android phone will NOT have root access. Meaning the system the system files can not be written over, hacked or deleted in anyway. The only area a normal Android user can access is the user home folder. Apps that you download can read the file system files, and that is it. Needless to say you will never get a virus.
The only time you can mess with the Android Phone is when you CHROOT it, meaning you become a super user, admin and can mess with your file system.
Take it from someone who has been an Ubuntu user for over a year and never had an issue with it doing all the crazy things Windows does. Android is Linux 2.6 it has a firewall and antivirus built in the kernel.
There are some badly written apps out there that can do things, but you can be 100% sure that they will never mess with the core of the phone. If its a bad app or you are unsure of it dont' install it.
The funny thing I see on the TV today was an Android Phone selling with Norton Antivirus, its a big joke, they are trying to get money out of you all who are so used to Windows PC's and the many viruses they harbour.
Word of advice, ANTI VIRUS on Android Linux devices is a waste of time and money. Period.!!!!