The bigger issue is the role of professional societies. Since I straddle various disciplines, I’m a member of four, in decreasing order of cost, IEEE, ACM, SIAM, and CAGIS. My following discussion is restricted to IEEE and ACM since SIAM and CAGIS don’t exhibit the same problems.
The vast majority of the IEEE and ACM membership are “practicing” professionals. The role of the small minority of academic members seems to be to freely produce papers for consumption (at a price) by the industry people. Initiatives by these societies principally include new insurance offerings and more finely graded levels of distinguished membership. Initiatives valuable to academics that IEEE and ACM did not provide include, as mentioned by others, EasyChair and DBLP. Their news feeds are aimed squarely at practitioners. I get academic and intellectual news, for free, from other sources.
The professional societies are particularly bad for interdisciplinary research. Ignoring the necessity to belong to several, even the individual societies are subdivided into an increasing number of subgroups, each having an increasing annual fee. This hits the practitioners particularly hard because academics can get the material through their libraries.
At this point, I’m a member of IEEE and ACM mainly because of inertia, and because my university might look askance at my quitting.
To be fair, IEEE and ACM have do some continuing good. I think that sponsorship is worth something, especially with the number of new conferences and journals announced each year. Also, small social groups w/o external guidance have a danger of spiraling downhill. That applies to fraternities, churches, social clubs, and university boards. That is not a current concern for SOCG. However if it happened in the future then ACM might step in, replace the board, and restart things. Of course, w/o ACM, academics in the field could also simply abandon the organization and form a new one. So, this is not a major concern.
Against that are the increasingly harmful effects that have been listed by others: the hassles, the cost, the difficult access to papers. SOCG leaving ACM is the first step towards a possible larger paradigm shift.