…and it is this: they do not become part of an online community. That may be because they don’t link, or don’t comment, or there’s simply no one else out there.
My 5 Stages of a Blogger’s Life hinted at this: there is a moment at which the momentum of starting a blog fades, and a new momentum – the regular input of community – is needed to continue. In other words: there is nothing keeping them blogging. The novelty wears off. The washing needs doing.
This is just a theory, and not founded on anything but a hunch, but I’m putting it out there for your thoughts.
Oh, and the implication: if we want people to have a voice, we might have to find ways to talk back before they give up.