All of us at this point have gone through at least one semester of design without taking typography. We've all committed terrible typographic sins. However, there is hope for our designer souls. Jim Godfrey has created a list of sins (and the proper treatment to repent) that perhaps we all should have on hand until these rules are memorized.
There are several things I enjoy about this poster. 1) The talent it takes to be able to purposely make bad type, and still make it beautiful (as seen in the header of the poster). He created an oddly arranged typographic header--and yet, it is still readable and in its own way--attractive. I think this could be a goal for all of us. To one day understand type "rules" enough that we can creatively break the guidelines and create ironically good type.
2) I enjoy the fact that this incited arguments between designers online. Reading comments about the poster, I've seen people that hate it, don't appreciate the humor, or think some of the rules are bogus. I've seen others angrily defend the rules Godfrey puts down. I just find it interesting that within the designer community, type "rules" still aren't totally universal.
Either way, I think the humor of the content is enjoyable, as well as the design.
A copy of all the rules is available as a pdf here.