Caydels SEO Blog is reporting that Google is recently testing a negative keywordfilter for AdSense after they already have the possibility to exclude sites by URL for a long time. This means you can fill out a list with keywords and AdSense will not display ads anymore that fit these keywords. While this may not be pursuing the same way the AdSense-Blacklist is treading, this should, if implemented, also be an effective means by which the average clickpirces can be raised.