There was a time when everybody knew their neighbors. While that isn't always true anymore, many people do live in neighborhoods that have been around long enough to have a true sense of community, or have worked hard to foster them. If you don't know or care about your neighbors when they're there, then maybe you won't care once they're gone, either. Or you might think that there's not really anything you can do either way. However, a lot of communities around the United States aren't willing to just look sadly at that abandoned house and hope for things to get better. They take action.
If you live in a community with a homeowner's or neighborhood association, it's probably easier to do it, but individuals can do it too. Sometimes it's as simple as one person mowing the yard and trimming the bushes of the abandoned lot next door, or picking up the free papers that pile up at the end of the driveway. Associations may form a task force to organize clutter cleanups or even change out seasonal decorations to make it look like the house is still occupied. That might sound silly at first, but if you know that theft and vandalism is a real possibility, it can be a huge deterrent. Community members may also do the legwork to contact the lenders and call them to task to take care of the property.
Sometimes the neighbors are the ones who let the local governments know about abandoned properties -- they don't have the resources to keep up with all of them otherwise. That leads us to laws concerning abandoned homes. Plenty of places have them but don't have the resources to enforce them -- and that's where community organizations can come in, too. However, some cities have found the need to pass or tighten laws that make it very attractive for owners to keep their houses looking nice, even if those owners are banks. Some charge a special fee for abandoned properties, levy fines if houses fall into disrepair or even ban plywood on windows.
If you can't keep people in their homes, you can at least keep the homes looking good. That makes the neighborhood safer and makes those homes more attractive to potential buyers. Speaking of potential buyers, filling those abandoned homes should be the ultimate goal for any community. And it's not impossible.