KenB - 4:27 pm on Aug 22, 2006 (gmt 0)

The thought that the problem with many sites dropping in SERPs has something to do with off site factors (e.g. backlinks) makes lots of sense to me. I know that there are literally tens of thousands of backlinks to my pages but Google isn't showing any backlinks from time to time. Its almost like Google is doing a massive data refresh and doesn't have backlink data for some sites.

Think about how quickly some sites dropped in the SERPs. Almost like there was a massive purge of data and then just as quickly some sites returned (e.g. a massive push of new data).