Something we noticed this morning is Google AdWords showing a URL in the headline of an advert:

It looks like Google is:

1. Only adding the URL to the headings of the top 3 adverts
2. Not adding the URL if the advert is taking advantage of the recent 'top ad' layout (where the first line of the body becomes the second half of the heading)
3. Not taking space or characters away from the headline to add the URL

This is definitely in testing phase right now as doing the same search a few seconds later did not show these results.