Tried a test on webpagetest.org because I got complaints that new WordPress site was running VERY slow. Seeing b.scorecardresearch.com and ds.reson8.com were causing load times to be 3x slower.
AddThis appears to know about these "cookies" (malware) and yet they still haven’t done anything to remove it: http://support.addthis.com/customer/portal/questions/3037805-scorecard-research
I should note that, once I removed the AddThis plugin, the above "cookies" disappeared and my page load time was MUCH faster.
Cannot rate higher than one star. Disappointed.