FB seems to have (rightly) realised that this is one of those 'just because we can, doesn't mean we should' cases, especially given the current situation. It's a bit of a non-story, and if I squint I can see the possible academic value in it, but given how battered FB's reputation is right now it's definitely not the time to try something like this.

I am sure that the privacy issues could be overcome with a properly run experiment, however there probably needs to be some rigour around that (possibly more than what was going to be provided given FB's history).