Here's how it starts-you have a question about something you need in your community, like someone to fix your garage door or roof. You want a personal recommendation, so you join one or more community-based groups (like on Facebook or NextDoor). You get the recommendation, you get the thing fixed, and you get on with your life.Only, you forget to quit the groups, and then you start seeing posts that prove, without a doubt, that your neighbors are...