Interesting article ...

Filters Force Spammers to Use Gibberish
(25 January 2004)
Though the incidence of spam may not be decreasing, the coherence of
the messages is definitely decreasing. Spammers who wish to evade
filters must garble their messages; most people are unlikely to open
e-mail with subject lines full of gibberish.

http://news.com.com/2102-1024_3-5147038.html?tag=st_util_print