I don't take this to imply "forever" necessarily. The grudge can end when the (alleged) wrongdoer pays for his deeds. Regardless of its actual effectiveness, i

I don't take this to imply "forever" necessarily. The grudge can end when the (alleged) wrongdoer pays for his deeds. Regardless of its actual effectiveness, it's a useful deterrent, along the lines of massive retaliation (http://en.wikipedia.org/wiki/Massive_retaliation http://en.wikipedia.org/wiki/Massive_retaliation).