I dont think that we can ever really know, about the number of lurkers...what I do know tho, is that if my own personality is indicative of anything, very often people are reluctant to get into very heated conversations, which is what is very often seen on these Evo/Creo/ID threads...
I have often been tempted to say something on a thread, but have held my tongue, because, I am more often in a rather 'timid mouse' phase, and actually do fear getting flamed or called names or such...tho I have gotten into some rather heated disagreements with some people, and have found it unpleasant to be called names...(tho I often have to remind myself, that being called names by a poster, who I deem as being 'whacko', is of no consequence)...now I am not using 'whacko' as being an instance of name-calling...I am merely using that term to denote someone who posts things which make absolutely no sense, those who posts hit and run insults and then run away, or those who constantly lie about things and then deny it....to me, they are beyond reason, and beyond discussions...and hence, 'whacko'...
So I guess the number of lurkers to FR will never actually be known...but to my mind, better to err on the side of there actually being many lurkers, and its better to provide them a lot of actual facts, rather than a lot of twaddle...