How do you keep people from stealing your writings and publishing them themselves when you post for critiquing

Post them on secure sites. Dont just post them on a blog or something like that. When you post it there will be a time stamp on the doc for when it was uploaded.

There's no way to be sure someone won't steal your work--esp. when just posting online.

When it comes to editors, it's the same worry.  Although, they really don't have a reason to steal anything, and i think it happens seldom.