If they are so mainline how come I've never heard of them?
Exactly. I find it very telling that the one line blurb that you get if you Google them, states that they are a "mainline" denomination. Who are they trying to convince? The truth is that they are just another wishy-washy, two-bit liberal/ecumenical group, with no real, uncompromisable, core beliefs, trying to make the rest of us believe otherwise.
In terms of membership, they are a relatively small group. They claim 800,000 members while the Southern Baptists claim 16 million, the Presbyterian Church USA claims 2.4 million and the Assemblies of God claim 1.6 million (to name a few). So the bottom line is - Who really cares what they think?
Good question. Me too!
. . . with the Roman Catholic Church
Among those churches which are not members of the WCC, the most notable is the Roman Catholic Church (RCC). Since 1965 a Joint Working Group (JWG), co-sponsored by the WCC and the RCC, has met regularly to discuss issues of common interest and promote cooperation. The group meets annually. One of the church and ecumenical relations staff members serves as co-secretary for the JWG and helps to coordinate contact between the Council and the dicasteries of the Vatican through the Pontifical Council for Promoting Christian Unity. [And] . . . Though the Roman Catholic Church is not a member of the WCC, it is a full member of the Faith & Order Commission. The RCC also serves the team on Mission & Evangelism in a consultative capacity.