I have been thinking a lot about social-networking sites such as Myspace, Bebo and Facebook recently, and my conclusions run along the same lines as Josh Harris in his article My One and Only Week on Facebook. That is, I personally avoid getting caught up in them because I find it a great temptation to waste time. I waste enough time as it is without spending hours updating my profile and uploading photos.
I guess this is also a good time to say sorry to all the (many!) people who have asked me to be their friend on Bebo. I am your friend in real life, honest! But I've consciously decided not to get a Bebo account, as myspace and facebook consume enough of my time.
Speaking of time, a large influence on my thoughts these days is this wee sermon by Jonathon Edwards, with the title The Precious Importance of Time (And The Importance of Redeeming It). It challenges me every time I read it, which can only be a good thing.
I have different (and less noble) reasons for not writing on people's "wall" though, because I simply don't know what to say! I find the idea of saying something to someone, but knowing that potentially the whole world is going to read it, quite funny, and a little scary. The short story is that I feel pretty awkward about writing stuff on people's sites, I'd much rather send an email or (if possible) talk face to face.
Josh Harris says his experience on Facebook "encouraged me to think about me even more than I already do," which is something I haven't found to be the case. I wouldn't put this as a reason why I'm not doing it, though I can see how it would work. Maybe it's because I think about myself heaps as it is, so these sites don't add that much to it. But I think a larger reason is that I haven't made much effort at developing my sites and trying to get people to be my friend, so it'd be silly for me to be too worried about what people think of me based on that.
Anyway, this isn't a dig at anyone using those sites, just my personal views on it, and a defense of why I won't comment on your site. I think it is worth questioning your motivations for doing it though, and I'd say doing it 'to fill in time' isn't a good enough reason.