Are you safe with a free anti-virus?

Do you really need to pay for an anti-virus program if you're a home user when there are several free programs available. Symantec says yes.
Well, I've seen computers running Symantec anti-virus infected with malware (a more generic name for any sort of malicious program- virus, Trojan, spyware, worm), and come across posts on the internet from people in the same situation. Having Symantec anti-virus does not mean you'll never get infected. Symantec will get rid of any infection for you, but you'll have to pay $99 if it's not one the program can handle automatically. That's on top of the original purchase fee.
Are you any less likely to get infected with Symantec (or any of the other paid anti-virus programs) than if you're using a free anti-virus program?
Honestly, you can get infected running the best anti-virus in the world (whatever that is) if your security habits are bad, and stay safe with the worst if your security habits are good, but judging by detection rates, the free anti-viruses offer good protection.
An additional advantage of avast! is the excellent forum: if you do catch something nasty online, you can get help to remove the infection for free.
The advice here is to use a free anti-virus for home use and save yourself the fees. Links can be found in the Security Watch article linked to above.