chrisuk - 11:04 am on Nov 9, 2006 (gmt 0)

You would think not if you use redirects but thats not always possible, however if all your links go to a redirect perhaps that is a flag also. Equally if your landing page contains advertisement text perhaps they can detect that, as presumably the same text appears elsewhere on other sites. Then maybe they weight the ratio of page content vs ad content and look at things like link structure and so on.

Site profiling may also be a factor would would explain why big brands can run all sorts of useless ads.

Its obviously a mixture of things that count.