Someone in a message board I read was complaining about "trolls" - in this case, the context was a discription of users who indicated interest in a reading group and then failed to participate when the time for discussion came around.
This usage puzzled me -- for me a "troll" is someone who deliberately makes inflammatory posts for no other purpose than annoying other users; i.e, there is an actively disruptive element to this kind of behavior.
For the situation at hand I would be more inclined to use "lurker".
Am I behind the times? Is the meaning "users who refuse to participate/contribute" familiar to anyone else, or is it simply an idiosyncratic usage?