At its peak SDS had about 100,000 members with organizers all over the country. They were active in civil rights demonstrations in the South, and in organizing poor people. Tom Hayden, probably the best known member, lived in Newark for four years organizing. Their manifesto, the Port Huron Statement was done in 1962, which, by any standard, was way early to be talking about "participatory democracy" and overly powerful corporations and governments.
Based on released FBI files, yes, no matter how paranoid they were, the government was doing more than they thought. Some SDS members were followed 24 hours a day by FBI. No joke. Towards the end, the Weathermen broke off from SDS and three of them blew themselves up making bombs.
Several things struck me. SDS was considered way radical then, and yet, how UNradical the Port Huron Statement seems now! Or maybe I'm just an unrepentant Leftie...
(Also, the Green Party Ten Key Values is similar to, and no doubt, owes much to the Port Huron Statement)