A period of unusual harmony when someone adds a new friend to their Friends list and immediately goes on a spree of liking and commenting on all posts and photos of the other. It usually survives for few months when things are at their sweetest and wanes out gradually.
SB: Nev, did you notice Dev and Kev liking and commenting everything on each others Facebook page?
Nev: Oh yeah! It's called Facebook Honeymoon. Won't last forever!!