Google is now providing a placement performance report that shows what domains/pages are driving traffic through your Adwords content network campaigns. This is very helpful in determining where garbage traffic is coming from. Sites that are driving a lot of traffic, but are not converting well, can be excluded from your campaign and your ads will no longer show on those sites. This report can be run at the site or page level, so you can be very specific about the pages you want excluded from showing your ad.
This report can be accessed through Adwords Report Center.