The unheard from...
I would suspect that some are members who have not logged on. As such they would show up as guests.
Others may not have the required e-mail address.
Still others will be as Cris has pointed out, observers. The in-the-background observers secure in their faceless, electronically hidden, voyeur driven witnessing of what goes on. Perhaps this is a little harsh but you can only guess at the silent few who leave no trace other than a number.
So what is their interest if not to contribute? Some we may speculate to be potential members, checking out the scene. But the numbers do not seem to reflect that all would be so. It is just to consistant!
And it strikes me as how unusal this thread is. The observed commenting on the observing. Almost as if the actors were commenting on the audience.
For those who read and do not particpate, do not grumble at what you read here. You do have your chance/choice to get involved and make your points and thoughts known. If you do not agree with what you read in these forums no one will know without particpatition!
I would further agree with Cris that we need quality comments and observations. It is what drives the forums to be great or small. Also I have commented on it before that new blood, so to say, is the driving force that prevents staleness. So every effort such be to welcome the new member who wishes to comment.
So, once again I also find my viewpoint in line with kmguru in this matter.