My students' biggest problem is simply leaving their type in the default font: Myriad. Their second biggest problem is that when they finally do discover the ability to change the font, they choose one of these awful fonts: Comic Sans, Papyrus, Party LET, or Zapfino. I don't blame them. Most inexperienced designers do. (Including those yahoos behind Avatar.)
I'm going to hang this prominently in my classroom to subliminally influence my students' typography.