I don't know which tag it is exactly that's doing the job, but here's what I have blocked in HOSTS:
127.0.0.1 adserver.adtechus.com
127.0.0.1 pagead2.googlesyndication.com
127.0.0.1 googleads.g.doubleclick.net
127.0.0.1 pagead2.googlesyndication.com
127.0.0.1 engine.spotrails.com
127.0.0.1 flash.quantserve.com
127.0.0.1 app.scanscout.com
127.0.0.1 cdn.livestream.com/widgets
127.0.0.1 google-analytics.com
127.0.0.1 cc20.adotube.com
127.0.0.1
www.adotube.com127.0.0.1 static.scanscout.com
127.0.0.1 dc.tremormedia.com
127.0.0.1 b.scorecardresearch.com
127.0.0.1 livestre.am
Since the other posts in here have become outdated, new users can use this comfortable in the knowledge that it works in April 2011 at least.