One way I know they don't delete stuff is that I cleared my entire history using delete buttons. Unfriended everyone, removed all the events, etc. The account looked clean. I also cleaned the ad categories or how they call it. It's interests they gather from your activity that they use to serve you ads.

When I came back a few days later my ad interests were again filled with stuff obviously deduced from my posts that I deleted. Things I no longer care about, but posted in 2010, and obviously not visited recently, so they have no way of knowing what those interests are.

Facebook is engaging in scummy activities obviously. They call most of those removal buttons "Delete", not "Hide". They just lie left and right. Data take out should instead be called data poop out, because that's the quality of the format you get of the data you provided them over the years.

Actually that may be one of the less legal things they do. If you explicitly ask them to delete particular photo or whatever, they should delete it and not keep it to themselves. There may be for example issue with copyright. What if I posted something I don't have rights to and want to remove it? They obviously don't have right to it either, because I couldn't have given it to them.