"Google's free services are being heavily exploited by spammers to redirect visitors to sites touting knockoff designer drugs and scams, according to the latest rankings from Spamhaus.org, a group that tracks unsolicited commercial e-mail.
...."

http://voices.washingtonpost.com/securityfix/2009/01/google_now_4th_most_spam-frien.html

quoted from Security Fix Blog