If you want to learn more about the relationship between you average CPC (cost per click) and AdQuality score, and how those might be influenced inversely by way of ad extensions, check out this great article by ClickZ:
In a nutshell, as you leverage ad extension you you ultimate goal is to improve conversions as well CTR. Google ocourse wants both as well. Higher CPCs yield more ad revenue, while conversions keep advertisers happy.
So, ad extensions such as Sitelinks (one of my personal favorites) are essentially designed to do both. An interesting sideeffect of this is an improvement in your AdQuality score (because your CTR increases). In turn, your CPC decreases, a nice bonus. Over time this benefit will most likely diminish as more advertisers take advantage of the features. Therefore, being an early adopter of these types of technology can yield some nice benefits.
So it is more important than ever to ensure you stay up to date on the latest trends in the industry.
On a side note, this is my first post made from my iPad, and I’m doing soLin the airport waiting for my flight.