3 August 2011
Recently some examples turned up of meta descriptions* occuring in AdWords ads without the advertiser using the exact meta description text in the AdWords ads. It seems that Google is testing this. If a natural search result (read: meta description) has a higher click-through rate (ratio between impressions and clicks) than an AdWords ad Google is obviously very interested to insert the meta description in the AdWords ad. A click on an AdWords ad finally brings money into the pocket and a click on a natural search result doesn't.
* A meta description is part of the source code of a web page and is a brief description of the content of this page.