Mumsnet is not a private members club, it's a public forum. I'm sad if people feel they have to go because of stalkers or other personally-directed unpleasantness, because that is unpleasant and not what forums are meant to be about.
But if people want to leave because things are not the same as they used to be when there were only a dozen people, and you could leave your door open all day, and it was all fields round here .... well, off you go then!
Change happens, deal with it.