Sadly, this looks like one more step in the walled garden web direction, somewhat like AOL sites back in the day. I am amazed publishers are apparently going along with this. They must be very desperate for views if they are willing to relinquish this much control.
I for one am hoping that this catches on, walled garden or not I'd rather spend my time reading content on an interface that I don't have to fight against (e.g. full screen overlay ads with a tiny x to close) and I trust facebook to build that better than anyone else. I'm also surprised publishers are going along with it though, it seems a little ironic. The only reason this product is interesting is because so many…
It's activated by clicking the icon or by using a keyboard shortcut (cmd+shit+x). So there is at least one single way to close any overlay on any website.