A likeaholic is someone on facebook who likes everything they see. Instead of writing a more meaningful comment, they press the 'like' button. This becomes an addictive quality in the person and they are known widely across the internet for it.
"Look at these pictures from Jane's prom! I am going to like them all"
"You're such a likaholic"
"Hey did you read my facebook status?"
"Yeah, I always 'like' them"