Lawsuits against companies for illegal spam also reduces spam.
in 2003, I filed a spam lawsuit against a drug spammer in Florida. Shortly after I settled, the amount of spam I received went down by about 50%.
I filed several spam lawsuits between 2013 and 2014. The e-mail load on my mail server went down by 75%.
Between May 27 2013 and Sat Jul 18 2015 (782 days) my server processed 4,801,196 e-mails (6,1397/day).
In 2012, my server typically processed between 20k-22k e-mails per day.
Between Aug 11 2008 and Nov 29 2008 (110 days) my served processed 1,419,128 e-mails. (12,901/day) But In 2011 I more than doubled the number of e-mail users.
When you sue the advertisers, they may terminate some of the spammer and the advertisers get some of the money from the spam networks that they use. At the very least, spam lawsuits get you on the spammer's suppression lists.