Even marriages can be extremely abusive...
The assumption that people on your friend's lists, Steam or anywhere (even just people in the same household) should be able to see your personal information, such as computer use, is a bananas assumption. It is an assumption that I'm pleased to say has failed privacy reviews at at least one company larger than Steam.
If you want to guess how most of the userbase would react, just imagine how much the average user would care when you told them about this "vulnerability".