There are reports over at DigitalPoint forums that AdLinks in a normal Ad-Unit? Basically, AdLinks which was released back in Mid March 2005, is an ad unit that just has links to a AdWords landing page. Some people opt for it in place of navigation, to encourage additional clicks. There are many strategies for its use.
But most people consciously opt for normal ad units to be placed in certain areas of a page. The reports suggest that Google is testing AdLink units by replacing a normal ad type with an AdLink. I certainly hope that is not the case. Three different DigitalPoint Forum members have said they have seen this happen.
Forum discussion at DigitalPoint Forums.