Not trying to make light of this topic, but 
sometimes people may forget to sign their name at 
the top.  I did it once and felt kinda silly 
afterwards. :(  But it wasn't about anything 
important so I guess that's alright.

For the most part though, it looks like people do 
it on purpose.  Though just remember, sometimes 
that anonymous post may be from someone who was 
just too eager to get thier message out and forgot 
to sign their name.  Doh!  Now I feel so silly. :)