Originating in halo 3 online, it originated when an american was unable to defend himself from some abuse i gave to him...
Halo Player: no, you're garbage!
Cill: You are the worlds greatest lifenoob!!
While he often said it to people in real life, it was first posted on the 'net in a comical thread within the forums of the MMORPG entitled "The Matrix Online". The original poster was (me) wwWizard2k (I claim the coinage of this word, it's not here, or on a basic google search =P), who had lost his cool at the lack of community, and decided to rant off some advice to his peers with a Sunscreen parody.
Meaning 1: Someone who fails simple everyday tasks. For example - failing to operate an ATM, tie ones shoes properly or wash their hands after using the toilet.
Meaning 2: Someone who fails to socialise in a normal way. For example - at a pub or club, attempting to use a pick-up line on a girl.
Meaning 3: Someone who can no longer function properly in a real environment, and must live constantly "online" connected to their computer/mobile phone/television/etc
Ben: Hey baby, wanna come back to my house for a drink? I've got cable TV
Ben: ouch. Hey sugar wanna come back to my house for a drink? I have a BMW
Ben: yeow. Hey honey wanna come back to my place for a coffee? I own stocks in a multimillion dollar company
3: "Holy shit. Those two fat geeks do nothing but play World of Warcraft all day, I bet they've forgotten the real world uses dollars and when you die you don't respawn."