Marcia - 11:44 pm on Jan 5, 2005 (gmt 0)

Couple more:

What a lot of it might point to, both internally within sites and with inbound links, is looking carefully at percentages of identical anchor text.

Also, if sites drop way down in spite of having lots of IBLs, particularly if some are sitewides, look at what portion of the page those links reside on.

It bears repeating and even more so now - in fact, it's critical now. If there's more than one domain name pointing to a site, make double sure they don't all return a 200. With all the page scraping going on, all it takes is one picking up on that secondary domain name and linking to it, which CAN appear as a link on the same scraped page as the link to the *real* domain name, and they'll both be identified and crawled, with the identical content for two or more domains.