One anti virus program is ok for the home user that doesn't do much. Just general surfing and e-mail. The big downloaders need at least 2 firewalls and at least 2 anti virus programs.
I have been to many a customer and had cases where avg doesn't pick up a virus and norton does, and vice versa.
Whilst I admit thet AVG is a good program, you will never know how good until you get a virus

And when it doesn't clean it, or cannot heal the file, where do you go ?
And if everyone in the IT Industry will tell me that Norton's is shite, what will they tell me to use ?