I'm going to say that a content-less post, or one that people cannot see the point of without outside explanation, qualifies. This includes posting absolutely nothing but an image (especially without any sort of context), and two or three word ALL CAPS LOL RANDUM posts that have nothing to do with anything but effectively the first words to come into your mind. There are forumites who do almost nothing but this and it encourages others to join in.
Hit the nail on the head there.
I don't like it when people encourage stuff like that. 'Cause if that catches on then we got five thousand people going "LOLMEWSPEW" I don't know what it means but it sounds bad.
That's why we got Twitter. For people who can't spell.