Not to be morbid, but I found out a friend/former co-worker of mine passed away via Steam. He had been offline for a super long time and one day I saw his account pop up as in game. I decided to say hi, only to find out it was his son. The son told me that my friend has passed about a year prior and he had taken over his father's account.
It was such a shock I had to sit and contemplate it for a while. I still don't quite believe it to this day.