Why does Google include the URL's in ads?

Such as with AdSense etc

[Visit Thailand]

I was just wondering why Google adds the url of the advertising Adwords client in their ads and on AdSense.

I know if you have banners it will only show an url if you have only one ad in the banner but I believe it shows the url for each ad in a skyscraper.

I was trying to think of the reasoning behined this but could not come up with anything wonderful. After all this could lose Google revenue etc. Any ideas?

[killroy]

Credibility of the ads and google, and preventing evil adwords adwrtizers from misleading visitors.

SN

[chiyo]

I would agree with Killroy. It gives just an extra bit of info about where you will go when you click the link, and probably increases CTR. If i see a well known brand name there, a domain name which seems to suggest the type of site, an "interesting" domain name, or a fairly authoritative URL, and not a multiple keyword URL, or a generic URL such as amazon, ebay etc etc, I would be more likely to click.

[jonknee]

I'm probably not the average user, but I always look at the status bar to see where a link is taking me. If I don't know, I don't usually click it.

The whole idea of AdWords is to provide high-quality ads to readers who want to see them. It just makes sense to give them a little meta data.