bird - 9:53 pm on Jan 25, 2004 (gmt 0)

if the number of links is abnormally high, and the quality of links (in terms of PR) is abnormally low, one has to think again.

Then why does Yahoo rank so well in Google?

It has an abnormally high number of backlinks.
Probably more than 99.9 % of those links come from pages with almost no PageRank (most sites linking to Yahoo are of the "me and my dog" variety).