Why pay when you can do it 'for free'?
Because free != better.
Just like Open Office is a very poor imitation of Microsoft Office full of bugs and incompatabilities unless you're doing very simple stuff.
As irrefutably demonstrated by a number of zero-day viruses that appeared on my radar this week, the free anti-virus brigade lag behind the commerical world in the speed of definiton releases.
It was interesting to watch.... some of the big names of the free brigade STILL haven't pushed definition updates to cover stuff that came out on Monday ! However in general they were 8 hours to a day behind the commercial guys.
Never used em, was once sent a free promo copy but it remains in plastic wrap to this day. They're not a big name, and I think the bank statment was likely a sales pitch ! Places like banks like the saftey of names they know and can easily recruit techies to maintain for.
I would suggest F-Secure. Or if you insist on going free, the Microsoft offering, because at least it's got Microsoft's bulgeing wallet behind it ! (note that neither of these recommendations are based on my comments above about zero day, because it varied which vendor picked them up first, Symantec and F-Secure did fairly well from memory though).