Source : Free On-Line Dictionary of Computing

Get a life!
     
         Standard way of suggesting that someone has succumbed
        to terminal {geek}dom.  Often heard on {Usenet}, especially as
        a way of suggesting that the target is taking some obscure
        issue of {theology} too seriously.  This exhortation was
        popularised by William Shatner on a "Saturday Night Live"
        episode in a speech that ended "Get a *life*!", but some
        respondents believe it to have been in use before then.  It
        was certainly in wide use among hackers for at least five
        years before achieving mainstream currency in early 1992.
     
        [{Jargon File}]
     
        (1995-01-18)