via Ajaxian (of course):
Developers all over the web are discovering the powerful new features that using Ajax lets them implement. Unfortunately, there's also a downside for some people associated with the web, namely advertisers, and how Ajax works. In this new article on the ClickZ Network, explores how Ajax can wreck havock on any normal "counting" system.
I've been very vocal about the AJAX counting issue; I've written several articles, spoken on panels, and pushed the IAB to update the impression guidelines on a very fast timeline. There's been interest and response, and the IAB is beginning to act. But everyone involved in the process realizes this will take time. So today, my recommendations for how developers of AJAX Web pages and software applications that include advertising can deal with the unique counting issues. There are no guarantees. Final guidelines may differ from my guidance. But, I'll put this stake in the ground. Let's see if we can't pivot around it.
He points out the main issue, namely that Ajax goes around the standard "just HTML" navigation model and can cause much less distribution of an advertiser's placement. He does have a suggestion or two, however - deploying new Ajax-equiped versions of sites, modifying the existing architecture to support an Ajax-related model, or just avoiding the use of Ajax all toegther.
His personal suggestion? Make sure Ajax is really the way to go with your application (as it pertains to getting advertising messages across) before making any kind of leap.