I'm using Facebook as the example, since it's widely used. It might not be a huge deal, but if you leave your account intact as is, people can continue to post on your wall. In my experience what usually happens is that, "I'm sorry you're no longer here," messages appear every anniversary of the persons passing. Those messages make it into close family members timelines and sometimes the reminder just hits the person at the wrong time. Sometimes people can be cruel or thoughtless too, and will post about your suffering or something terrible which can be traumatic for the people you love. You might know all sensible people, but in my group I've seen some doozies.
If you don't want to delete your account, you could always have it memorialized instead. You would need to name someone as "My Legacy Contact" who will submit the information when you're gone. That person could decide where to go from there with your instructions for handling your account.