Someone who is always the first to shell out big bucks for the newest Apple product. May camp out overnight to purchase the product. Always ends up a guinea pig sorting through the early release bugs and never admits there's issues.
More generally, any person whose entire social life is based in cyberspace. I.E. hardcore Facebook, Twitter, Myspace, Warcraft, Sims, etc users and most bloggers.
That guy plays Warcraft 10 hours a day, claims to have 50,000 friends on Facebook, and never leaves the house except to get the mail. What an iPhag!