Realworld cemeteries can be the victims of vandals who tip over gravestones (often breaking the older ones), add graffiti, and litter. So far, there have been no signs that hackers feel any urge to desecrate on-line graves, but I suppose it could happen, and in a number of unprecedented ways, at that.
Imagine morphing photos, replacing a photo of your mother with that of a stripper, animating your grandfather's studio portrait to make him wink or flash or.... Imagine altering biographies, inserting invented sins or blaming others for things they never did. Imagine adding links to Web sites your loved ones would never have approved of. Imagine zombie or ghoul viruses, whatever they would be.
The possibilities are endless, and more than a little frightening.