Hi, ragingblur!
Some people can belong to any number of different organizations and still not be able to draw upon the fine references of people that they might need, nor be able to prove to others the reality of their own (what they might perceive themselves as) fine worth in order to seek out other employment opportunities.
If a person proves to others that they are indispensable at doing whatever type of job they have and are a "team" player if they worked with others, then those sort of accomplishments and attributes should be easy to demonstrate and subsequently be able to prove in the course of an interview.
Also, if there's more "fluff" rather than "stuff" on a resume, then if I were an employer, I would be more likely to be suspect of a person who listed too many group affiliations as maybe needing to "pad" the resume to make themselves look better.
Not that it's totally bad to list that particular affiliation because, as has already been mentioned, it's situational. But, if it were me, then I would be concentrating on making the space available for listing what I've done as an employee or self-employed person rather than the organizations to which I belonged.
What sort of employment have you already had and what type or types of employment are you seeking, please?
Thanks!