Even sending a happy birthday message on Facebook can help keep you top of mind.
What makes communication awkward are the long periods of silence in between. Even though people are ambiently aware of each other, they still need to follow up.
A quick text, a like or comment, an email, or better yet, a phone call or handwritten letter, keeps you relevant. Small acts of care help preserve relationships in the long term.
If anything, social smacking helps break the ice when you do meet again face to face.