I have personally ranked quite well on the few sites that I have with the use of primarily non-relevant backlinks. I think they are very good to have, after all in the real world what would be better for a painting contractor?
A referral from the paint store from which he purchases his paint and tools
or
A referral from the Doctor who's house he just painted.
Is the Doctor relevant content? I don't think so, but most consumers would believe the doctor or otyher homeowner long before they would take the word of the painting supply store.