Maybe someday LinkedIn will decide to let the users search for groups, or let group managers categorize them, so people can find all of the Perl groups easily. LinkedIn is a bit wary of people collecting groups like merit badges though, so I think this is a social control. You actually have to know the group people to into the group.
What's the next step? Maybe someone will hook up CPAN Ratings (or Testers or Testing Service) to LinkedIn so Perl hackers can have recommendations. Being an open source programmer tends to suck in the corporate resume world since recommendations don't come from bosses and such.