It might help to have a multi-dimensional system in which karma is measured by (k1, k2, k3, ..., kn). Let the reader specify thresholds for each, as they see fit. For example, k1 could relate to humor, k2 to historical insight, etc. If you're in the mood for a laugh, you'd increase your k1 weighting as you view the system. As for measurement, this could be partly by the votes of others who have high karma in the category.

Not that this matters much. I think people just stop reading various websites when they judge the site, overall, to be boring or useless. For example, if people find stackoverflow to be more informative than (insert name here) then stackoverflow "wins". Whatever winning means.