In case you missed it, AdWords made a slight policy change on display urls this week. You have to include the subdomain now. So if your destination url is blue.widgets.com, you have to display that, and not use widgets.com.
The post from Google doesn't define that precisely, but it appears they're talking about public domains like blogspot.com which could have zillions of different subdomains controlled by different entities.
Since long ago, I was seeing ads that would point to a Google Base page, and the display URL in the ad would just state google dot com. Totally crazy considering the trust that people have in Google's brand.
And then you get to the page selling who knows what. People should think they buy from Google?!
Everyone who is familiar with Google Base knows how easy is to create a landing page there.