I didn't mean to imply that he was only being negative on LJ -- I don't have a large enough sample set. However, behavior learned in one medium does seem to carry over into other media. I have a number of overlapping social circles who are centered on electronic fora, and in each circle the conventions that were converged to online tend to arise in FTF, and tend to color the people's behavior in other interactions (this is only really observable in people whom I know from multiple online circles). But boy is that an essay for another day, when I have more evidence...

Also, it was more of an observational effect -- that you see that other people post their negativity, and that in turn influences your behavior -- rather than evidence from his past journal I was going on. Not "you've been negative in your journal", but "folks are negative in their journals around here; you've noticed this in yourself -- perhaps it's one influence?"