I know of several people who have taken up genealogy in order to join one of the many lineage societies such as Daughters of the Confederacy (UDC), Sons of the American Revolution (SAR), Sons of the Republic of Texas (SRT) and the like.
I do have some cousins on my father's side who are members of the Daughters of the American Revolution (DAR) and if I wanted to, I could propably use that information to join SAR. I also probably have enough information on my mothers side to join SAR as well as other similar groups.
The main reason I haven't really looked joining any of these groups is that I'm not sure how active I would actually be. I realize that like any other group I can be as active as I want, but it seems to me that the main benefit would just be having a group legitimize my and others work. Right now my plan is to find and join some active, local genealogical societies rather than lineage groups. I think these type of organizations would be more beneficial for me at this time.