Link Popularity is described by Search Engine Teoma like this

“Instead of ranking results based upon the sites with the most links leading to them, Teoma analyzes the Web as it is organically organized—in naturally occurring communities that are about or related to the same subject—to determine which sites are most relevant. To determine the authority—and thus the overall quality and relevance—of a site's content, Teoma uses Subject-Specific PopularitySM ranks a site based on the number of same-subject pages that reference it, not just general popularity.”