Hee hee! I think lots of LJers do the same thing. I certainly do, I mention it one of my posts today (the chainreading one). I agree with hornedhopper that it's not so different from planning things to tell your family or friends when you get home (or as hornedhopper said, at the "lunch table").

"You've all got to hear this *insert carefully planned out retelling of incident*"

It's just that maybe since we're actually writing/typing it out, we're a bit more mentally aware that's what we're doing.