As a counterpoint, my experience has been that this is only effective if you are looking for a position that is already in high demand. It's relatively easy to go to a meetup and meet other engineers who will recommend you at their company when it inevitably comes up that more engineers are needed on the team. In other positions like, say, marketing or finance, it just doesn't happen that way nearly as much. Postings will often get hundreds of applications within a few days and having a casual acquaintance from meetup-type groups is of little benefit compared to desirable brand names and keywords on your resume.