The interesting bit is that social expectations matter.

There is a social expectation that people can generally only enter your home with explicit permission, and so if they didn't invite you it's trespassing even if the door is unlocked. But maybe you have some close friends who you get used to coming over and just entering even if you may be out at the moment -- and then it's not trespassing anymore.

Remote computer access is a much younger phenomenon than people living in houses, and so social expectations aren't as established. There's a legitimate need for discussion there.

For example, if you have an open webserver that you want people to access, is it trespassing if people fiddle a little with the URLs and encounter documents that you didn't mean to put out there? I'd argue it would make for a healthier and more tech-savvy society if we didn't consider that trespassing.

If we try to push the houses analogy further, it's a bit like inviting people into your house for a big party, and then somebody enters a room that you didn't want them to enter. It's a faux-pas, but you'd probably also have a hard time if you tried to label it trespassing.