I think some people look at other peoples profile by accident, I know that when I click on a thread I sometimes click the persons name that last posted and it takes me to their page, but that is just me lol. *shrug*
Maybe some people get scared to post or something? I know that I was posting alot and ending up posting somewhere I wasn't allowed and got a infraction which basically stopped me from posting in alot of threads to avoid getting another one. I had 99.8% activity at that time now look at me, I'm in the 40%'s lol.
I just lurk anymore because I have nothing worth while to say and from time to time I'll post something but rarely anymore.
That is a pretty good idea though Slayn, it might help avoid more lurkers - I noticed we had LOADS of lurkers in our Monster Hunter forums, so making a online gaming section could be fun.