A person who tweets and excessive amount on Twitter to the point where their followers are annoyed.
Person 1: Dude! I passed the Tweet limit today and I couldn't tweet for like an hour!
Person 2: You're such a twitter whore.
AFD for short. This is when a person becomes an uber fangirl/fanboy of whatever they enjoy to the point where they are fans of everything.
Person 1: Omg! I love Harry Potter!
Person 2: OMG YEAH! And I love Twilight and Star Trek and Lord of the Rings and Pokemon and sheep and chapstick and ipods and cheese and...
Person 1: You so have Addictive Fandom Disorder.