According to http://www.thefreedictionary.com/decay, you'll find that decay occurs in several areas of our lives. For instance, in Electronics Decay means to decrease gradually in magnitude. Used of voltage or current.
Unfortunately, in most every other way one can conjure up a mental picture of decay, the results aren't good. Death, rot, instability, degradation, ruin.
It should come as no surprise that we've got some major decay exposed in various governments around the world where dissidence is not considered cool by any measure. I've seen decay in my own country from its infrastructure, to its JUSTICE system where sneaky, underhanded, civil-rights-violating acts of treachery are committed in the name of Liberty, and The Common Good. Where do we draw the line?
Do we wait until the bridges collapse before replacing them with stronger, more modern ones? No, we try to address the problem before any damage is imposed on innocents. For the same reason, most people visit a dentist twice a year, so they don't look like they've got a bad case of Meth Mouth. Let's not allow America to come down with Meth Mouth, because we know better than that.
(pic unrelated?)