It’s the yin and the yang. If the product is free to you, you’re the product being sold to someone else, even if anonymously. Google for example provides a great amount of value for not charging any money, and we know going in it’s our usage/activity which gets sold to their clients, more-or-less anonymized (although not perfectly anonymized, because it’s possible for Google’s clients to apply some analysis to figure out my usage data). So on the surface of it, I don’t like AVG selling information about me, but if it’s anonymized, I care less, but it would provide something valuable so I would put up with it.
As it is though, I only run Windows for one specific purpose periodically (updating my TomTom), and my “antivirus” is Linux. (Yes, I realize it’s not immune, but it’s pretty darn good.)