I just got an advertisement from Avast. It used the same toaster window as update announcements (though it had a white background instead of green) and encouraged me to install Google Chrome.
A number of things bother me about this:
1. The classic definition of adware is any application which shows advertisements to the user. This can be benign, as in ad supported freeware, or it can be malicious.
2. I don't have Google Chrome installed on this computer. This leads me to believe that Avast enumerated the installed applications on my computer with the purpose of determining whether an ad for Chrome ought to be displayed.
3. I start to wonder what sort or metrics and tracking Avast is sending home every four hours or so.
Security software by its nature gets a free pass on a number of activities which in any other context would be considered a security risk. Things like phoning home multiple times per day, scanning the contents of system memory, redirecting OS APIs through its scanning interface, monitoring all network activity and blocking traffic which falls under its blacklist, and on and on. The tradeoff is that security software (in my opinion) are held to a higher standard than other software categories. This double standard is necessary to maintain the trust relationship between the security company and the user; my trust that Avast AV will keep my computers free of adware is seriously threatened if Avast itself is showing ads.
I'm not saying that Avast Software are now untrustworthy, nor do I begrudge them the ability to make tons of money from their awesome products. I'm merely pointing out that perhaps showing ads users is not a very good idea.