Ruin Criteria I: Dangerous?

This is the first in a series of posts that will address the central question of "What is a Ruin?"

There are many abandoned buildings within the built-up urban fabric of Jerusalem. Some of them are relatively new, some are in pretty good shape. Avid urban explorers might be tempted to sneak in and check them out - that's part of the fun of old, ruined buildings. To protect against this, abandoned buildings are often sealed off. However, sometimes the buildings pose enough of a danger that added warning is required, as in the President Hotel on Ahad Ha'am street. In the sign below, you can see this. I especially like the icon of the building collapsing.

Are ruins necessarily dangerous? I think that it's important that ruins be abandoned and that no one is taking care of them. I suppose this means that one day they will become dangerous. Let's say that the life cycle of a ruin begins when the building is abandoned, but only really gets moving once it becomes dangerous. That's when the structure starts to fail and the building starts to fall apart. However, on the other end, eventually the building collapses enough that it stabilizes and no longer poses a danger. According to this logic, a ruin doesn't necessarily have to be dangerous, but unless it either IS dangerous or HAS BEEN dangerous, it isn't really a ruin. Rather, it's just an abandoned building.