tedster - 11:19 pm on Sep 28, 2008 (gmt 0)

sites that have similiar content who also have backlinks from relevant sites

This borders on another territory that Google ventured into in 2002 - LocalRank. With LocalRank, the preliminary result set is then analyzed by restricting link juice to just those domains within those results. Then a re-ranking is performed over that preliminary set, based on the LocalRank score.

After six years, I'm sure that the straight-up localrank method has been assimilated into other routines, but the essential principle would remain - and be seen in authority calculations.