Well, from the examples you posted, it's kinda like a Facebook wall, except other people can't directly comment on your comment (unless they also post on the profile). It's like if you have something quick to tell someone, then VM it, if you want to have a long conversation that you don't think is private enough to stay in Private Messages, then that can be carried out over VMs and... that's basically its only use really. But yeah others can read those messages, it is basically like you said.