Not just viruses, even some anti-cheating measures on video games have that same ability.
Take World Of Warcraft for example, they have a system called "Warden" that can look at every part of your system and report what it finds. The idea is that cheaters can write their hacking software to look like anything so to stop game hackers, they need access to everything on your computer.
The TOS and EULA you agree to at the time of installing the software and you again do it on each patch gives Blizzard entertainment full rights to complete access to everything on your computer.
Now, you may ask what stops them from using this in bad ways?
Nothing but their integrity, oh and the integrity of every employee involved in that section of the company controlling Warden. The thing that makes Warden special is it is like a robot waiting for orders on what to look at, the orders can change from one second to the next so there is no real way to know what information is being gathered from your computer and sent back to Blizzard.
Data miners have been out for a long time that collect and sell information on things like browsing history and other things to try and help sell more things to the public, well this is certainly capable of that kind of thing without anyone knowing.
I guess my point on this is we not only have to be careful about the unknown viruses we might get on our computers but also we should be paying more attention to the malware/viruses/data miners, we intentionally install on our computers.