Also, at the time, there wasn't much you could do after having joined the group. This has changed with the recent introduction of discussions.
One of the first posts spurred some thoughts about the usefulness and goals of this Linkedin group especially given the high quality of our new mailing list. (And let me take the opportunity to sincerely thank T.J. Crowder for all the effort he's put into it.)
My initial reaction, based on an early August thread was to suggest keeping the development-orientated discussions in the mailing list, while expecting more career-orientated ones to take place in the Linkedin group.
Of course, there's no way we can nor should be controlling this, and in the end, you will be deciding what will happen where. So I suppose the only real raison d'être of this post is to advise you of this new feature and open up the debate.