leech

leech n.  Among BBS types, crackers and {warez d00dz},
   one who consumes knowledge without generating new software, cracks
or
   techniques.  BBS culture specifically defines a leech as someone
   who downloads files with few no uploads in return, and who does not
   contribute to the message section.  Cracker culture extends this
   definition to someone (a {lamer}, usually) who constantly
   presses informed sources for information and/or assistance, but has
   nothing to contribute.