This is all part of an effort from Facebook to make the groups more transparent and give a chance to group admins to see how many unwilling members their group(s) have.
Images play a pivotal role when selling a real-estate - buyers get a glimpse of their prospective new homes and decide whether they are going to buy it or not. Therefore, there's even more responsibility on the shoulders of real-estate agents if they publish their work on a social networking site that deals mainly with images.
