Source : Free On-Line Dictionary of Computing

dogpile
     
        ({Usenet}, probably from mainstream "puppy pile") When many
        people post unfriendly responses in short order to a single
        posting, they are sometimes said to "dogpile" or "dogpile on"
        the person to whom they're responding.  For example, when a
        religious missionary posts a simplistic appeal to alt.atheism,
        he can expect to be dogpiled.
     
        (1994-12-08)