I think I'm the one to orginally bring up the discussion on the emergent church because unfortunately my pastors/church are attracted to this. I say unfortunately because I have done quite a bit of reading in the last year or so and I discern the errors of this movement myself. What you bring up is a good question - What's wrong with encouraging community and discussion and such? And you brought up what's a major wrong in the emergent movement - theological error. Do you see the deception right there?? There's something that sounds good, but when you really read between the lines there is something else going on. After reading 3 + of Brian McLaren's books (who is a "leader" in the emergent church movement) and others I feel I have a pretty good "feel" for this movement and also spending time on some popular emergent sites. I see some strange things like confusion about homosexuality, abortion and such. The push for an ecumenical mindset and that "liberals are really fundamentalists too" - that is a quote from McLaren by the way. And I see a watering down of the authority of the Word and the basic gospel. McLaren is really big on Jesus and having authority in Jesus but he says nothing about the Word of God. Basically it's just another Jesus. I don't think Paul is a favorite amonst the post-moderns. McLaren does have some good things to say BUT then there's some very bad error and a lot of it is presented in a "sneaky" way - through strawman stories and ficticious characters, and this is where you start seeing his real bad theology coming through. There is no gospel presented in any of the emergent church stuff I ever look at. It's like sin and repentence hardly exist and are redefined. And the major error is the diminished authority of the Word of God. I'm waiting for someone like James White to jump on the band wagon more with this. He has had a little on some of his blog from earlier January. There are 3 web sites with a lot of information of the dangers of the emergent church:

http://www.challies.com/archives/000712.php
http://www.lighthousetrailsresearch.com/emergingchurch.htm
http://members.tripod.com/carla_b/emergentmovement/

They've done a better job than an me to explain the errors of this movement.

I've been a Christian for a while and have done more reading than the average Christian woman out there in general and I am very disturbed with reading the emergent church stuff. It's hard to put the emergent movement (and they don't call themselves a movement - it's conversation)in a nice tidely box. There seem to be different emergent churches out there. VintageFaith is Dan Kimball's site. I also read his book - 'The Emerging Church' . He seems to have a bit more of an orthodoxy than McLaren, but big red flags come up for me when he is quoting McLaren and other emergent leaders and he talks about stuff like contemplative prayer and the Taize movement (an ecumenical community in Europe) in a positive light. All said, everything I keep seeing just doesn't jive with Scripture.