I had quality scores of 10/10 for my kws in a campaign and average position of 1.1 for a while. Suddenly I open my account and I have a 7/10. The landing page is for a clickbank product that I don't own. I also did add another add group w/ differnet keywords. Could that affect it? Curious. This what they call the Google Slap? Thanks!
QS is a relative number of your quality vs. historical quality of your competitors. Main component of QS is CTR. It is also calculated taking position into account. In other words, your CTR is lower than what competitors have historically done at your position. Someone else has a better ad than you. What people call the Google Slap when talking about Adwords is their QS going down to 1 (effectively 0), although some may have their own, different, definition. Lately, this is happening to those with pages with affiliate product links.
Right, check for the development of your CTR, has it decreased a little lately? Also check for new adwords competitors on the result pages. Maybe there is a new ad performing better than yours now. Also keep in mind that if you split test new ads, if they perform with a lower CTR as your current ad, QS may also drop.