It makes sense to give your software out free, especially to novice users.
It is the reason why most "novice" users use Norton, they get 3 months "free" with their new PC and then they buy it cos it's what they know and trust.
Same goes for AVG, they give it out free in the hope that people that come to know and love it will then pay for the upgraded version with a few more bells and whistles.
Corporate companies use lots of different scanners. The company I manage the IT for currently use F-Secure, but it's a bit heavy on the processes, we did use Trend for a few years which was good, however I think I will look into the Corporate NOD32 client when it comes up for renewal again.