I dont think you can ever be 100% accurate with usage figures but just with downloads.But comodo does call home whether you allow cloud functions or not so some form of cloud tracking is in place.
Indeed, however I'd prefer a system that isn't optimistic, for example a system only based on people activating would be rather optimistic as if you install it twice then you'd count as two persons and hence we'd believe there are more users than there are. However if we change the question from "how many users" to "how many active
installations" then it'd make more sense but it wouldn't take account for the people uninstalling, so here we could instead see how many clients are actively updating and from that we see a minimum amount of active installations with the only possibility for there to be more (clients on disconnected computers)
I don't know, my head hurts...
Avast claim 180 million users although i dont think that figure is accurate by any means and is simply a selling tactic to make the product seem very popular when in fact the figures are probably based on email registrations.
If CIS has 50 million users then I think 180 million isn't so unbelievable for Avast. When I see threads that wants recommendation for new security systems on other forums, the majority recommends Avast and then a tiny few recommend CIS, but perhaps that's just the situation in Sweden. *shrugs*
Either way from my experience the numbers don't seem so weird in comparison to the CIS numbers, however the accuracy of these can of course be debated.