Not sure if this is something new, as it is the first time I have seen it when logging into Ancestry.com.  I decided to set it up and give it a try.  When I logged in via Facebook, I had to login also at Ancestry.com to link up the two accounts.

I guess this could be easier in the long run to minimize username/passwords to remember.  From what it says when linking that no information will be shared between Ancestry and Facebook.   I am not sure how this can or will be used in the future but wanted to let everyone know that its possibly new.