Someone asked this in an effective altruism Facebook group and I'm tired of seeing so many people not ask questions like this on the EA Forum when it's got a function dedicated to posting questions like that, so I'm just going to post them on the EA Forum myself. I'll post links to the answers to this question in the comments section of the Facebook post.
In cases where you do this, I strongly recommend linking back to the original question on Facebook. This lets people see any edits someone has made to the question + the answers they've already gotten (so that someone doesn't waste time writing something on the Forum that's redundant with something on Facebook).
It wasn't a private group but only people need to request to join if they're on Facebook. I agree with you though.