This is the most detailed disclosure I've seen from Yahoo - kudos to both Eric and Priyank for a very rich interview. I appreciated these comments about spam detection very much.
We use algorithmic and editorial means to fight spam. What we have found is algorithms are very effective at fighting spam at the large scale, and our human editors are very effective at recognizing new techniques and providing us that early signal, which we can use to scale-up the detection processes...
However, if there is a page that is generally okay but has some spamming techniques, someone might search for that URL, and as a search engine we want to make sure we have the most comprehensive experience we can.
Also, some nice information about paid links - Yahoo doesn't automatically discount paid links if the rest of the algo shows that those links add to the user experience.
[edited by: tedster at 9:14 pm (utc) on July 7, 2008]