I find that the ratio of reads to responses is normally around 10 reads per reply. Anything in that range seems normal to me.
We do have a slew of folks who just read, here. Any active web site will have a lot of folks who drop in regularly to see what's going on but don't participate directly. And there are a lot of members who have zero posts, too. That's the "Cloud of Witnesses" I tend to go on about, and it's one of the things that makes cyberspace unique. More power to them!
For the folks who do post, though, it can seem pretty cold when someone starts a thread about something painful, or something that's difficult for them to discuss, and it sits for hours with no reply. [I've pulled a whole slew of posts because of this, myself. It seems as though the more emotionally charged the issue, and the more I really, really, really want someone to reply, the more likely it is that nobody will. I do think that when people step outside their usual roles, it scares other people away. Unfortunate, but part of human nature, I guess.]
Ages ago I suggested - and a few months back I think I suggested it again - that when someone posts in obvious pain, and people who do routinely post - just can't think of anything to say - then, typing a few parentheses around that person's name - giving them a cyberhug, at least - is a whole lot better than leaving them only an uninterpretable silence. Like in realspace, when we pat someone's shoulder or give them a hug at times when words fail us. That's something we can do even if we're hurting, ourselves, when we read what they've posted... even if it brings back painful memories for us, surely we can at least manage a hug for them?
We'd do that much in realspace, in a heartbeat.