I just saw this article on the Planetizen website. It's about how Youngstown, OH is handling being a shrinking city, and intriguingly, it mentions that both the city and the university, Youngstown State, are buying houses from willing sellers as part of a land bank, an idea I'd mentioned. While the article's point is that shrinking isn't enough (to which I might add "yet"), I looked into the literature on land banking and sure enough, it's recommended practice for shrinking cities. In the same set of articles, I also got outside confirmation that Cincinnati is indeed shrinking. It lost over a third of its population between 1960 and 2000, and I would bet that percentage will be around the same when the 2010 numbers come out.
Most importantly, it turns out that land banking has been authorized in Ohio since 1976, and that Cincinnati has had a land bank since 1996. It acquires only ~10 properties a year whereas Flint, MI and Cleveland, OH acquire around 1000. In April, former Gov. Ted Strickland signed a bill authorizing land banks in every Ohio county (previously only Cuyahoga County was authorized to land bank on a county level, and Cincinnati's was a municipal enterprise). Expanding to Hamilton County would allow Cincinnati to take advantage of the extra money that could come from taking less-damaged foreclosed properties in the outlying areas and reselling them and using the profits for upkeep and redevelopment. Apparently, though, according to this Master's thesis from the regional planning program at the University of Cincinnati, the Cincinnati Land Bank has even bigger problems to sort out first.
This probably still would not help my grandmother, as condos are not particularly valuable land banking property, and she can still pay her taxes. Still, a new and improved Hamilton County Land Bank might be able to help with the zombie move malls.