To add to tedster's commments - I still firmly believe in trustrank with google. I agree with everything tedster says about the page and link being worthless under the wrong circumstances. But I believe that if you get an exact like-for-like link from a .gov and a .biz (i.e. identical pagerank, backlinks, topic, anchor text, number of outgoing/internal links etc. etc. etc. etc. etc.) there is a high probability that the .gov is worth more.
By worth more, I mean that if a .gov and a .biz suddenly created identical directories I could submit to, I would pay $100 to be in the .gov and $60 to be in the .biz
However: I would buy 100 .biz links rather than 60 .gov links if the links and linking pages were identical ... translate that in to time set aside each week to obtain links and there is a decent link building plan in there somewhere I think! ;)