One of my sites was penalized by Yahoo - when I asked why, I received the canned response about not meeting the content guidelines. One of the reasons they gave that sites are most often penalized was "Use of reciprocal link programs". However, in their own guidelines to get better rankings, they say to corraborate with other webmasters to develop a linking network of relevant sites (sounds like "get relevant reciprocal links" to me).
Any ideas of this seemingly contradictory instruction?