20 Feb Google Updates Display Url Policy
After much rumor and speculation. Google announced that effective April 1st (not the Google Hoax) the display url and the destination must be the same. Most ads are not affected by this change, mostly redirects and vanity urls.
From the Google Blog redirect urls are still accepted (if you use tracking urls) as are the use of subdomains (as long as the top domain is the same).
Adwords will also send alerts to the Adwords accounts before the April 1st date to let those accounts know if they have ads that are not incompliance with the new policy.