Improved sharing of .onion links on Facebook by Will Shackleton.
From the post:
Today we are rolling out two new features on Facebook to improve the experience of sharing, discovering and clicking .onion links to Tor hidden services especially for people who are not on Tor.

First, Facebook can now show previews for .onion links. Hidden service owners can use Open Graph tags to customise these previews, much like regular websites do.Second, people who are not using Tor and click on .onion links will now see a message informing them that the link they clicked may not work. The message enables people to find out more about Tor and – for hidden services which have opted in – helps visit the service’s equivalent regular website. For people who are already using Tor, we send them straight through to the hidden service without showing any message.
Try sharing your favorite .onion link on Facebook and let us know in the comments what you think about our improvements!
This is a very bad plan!
If you are:
not using Tor and click on .onion links will now see a message informing them that the link they clicked may not work.
and, Facebook captures your non-Tor accessing of that link.
Accessing .onion links on Facebook, without using Tor, in the words of Admiral Ackbar, “It’s a trap!”: