Rotating Ad Sense Ads on AJAX Calls?

Here is a link to an article discussing the ways you can reload google adsense ads when the user is doing something AJAXey, or really, whenever.

I wonder though if google allows this type of thing in their terms.  You couldn’t refresh the ad every 2 seconds, so why would they let you refresh the ad ever?  How could you define when you could and couldn’t refresh an ad?