Sharp as ever, Wulf quotes 2 Peter to suggest that Paul's language isn't always clear or simple. And having recently completed a short commentary on Galatians (due out in the Crossway Bible Guide series in mid-November), I'd have to agree.
My point in the previous post was a slightly different one. It is that Paul chose words to describe the gatherings and leadership of the groups he was planting around the Mediterranean rim that were not 'religious' but were drawn from the business and social world of his day.
After all, the message (euanggelion another case in point, as Philip notes) was in places hard enough. So Paul appears to have been keen to put no stumbling blocks in the way of people hearing and having the chance to respond to that message.
Sometimes I think there's a danger that we do the opposite: our language about membership gives the impression that the good news about Jesus is for a special group of enthusiasts who know what the words mean and we use those words to exclude rather than include.