It always seemed to me that it screams of insecurity when two people have a tremendous need to let everyone around them know of their love for each other.
Whether it is public displays of affection or public posts on Facebook.
Unless it is an actual announcement such as an engagement, it should be enough to just let each other know how much you love them.
What they are doing whether it be the constant need for publicity or the speed in which they feel in love, it certainly spells out addiction rather then love.