'Dark Social' is on the rise again more specifically Facebook inApp referrals on iOS devices. I started the investigation having noted PVs/Visitor for referrer type: typed/bookmarked (no referrer) in significant decline from around the start of September.
As we're measuring Facebook app traffic using method detailed in Ben's blog I was able to run the following which shows Facebook App no. of unique visitors trended over time for referrals from social and typed/bookmarked.
The above highlights the aggregate no. of uniques have remained around the same, however there's been a shift in no. of uniques being associated with each referrer type.
I've not yet come across any information which details the change, but am sure some will find the above useful/informative.