In social media world, posting some final "xyz has passed on. this account will be closing" or similar 'wrap up' activity is often useful.
I couldn't even cancel the health insurance company's recurring payments after a death. And they had the audacity to send a "how was your hospital stay" questionnaire to the account holder's email after they were "discharged" by the hospital.
That feels like an email that deserves an honest response:)
When something like this happens, you lose your mind slightly, and you become obsessed with preserving whatever is possible to preserve of the person. I went so far as to record his voice-mail message, just because I felt i needed to.
Of all the internet stuff, the thing that was most important to us was photos: he was a photographer, and he used a photo-uploading service (I think it was Google Photos, but I'm unsure, it's been a couple of years) and I was able to get an archive with all his thousands of photographs.
Eventually, I put everything I could possibly find (computers, internet services, whatever) into one big zip file, and put it on my local NAS (which is backed up to the cloud). I don't think I'll ever have the heart to go through it again, but my brother had young kids who never really got to know their dad. I figure one day they might want to look at it (even if it's 30 years from now) so it makes me feel good to know that it's been preserved.