Bart Ehrman said in his Fresh Air appearance today (starting about 13 minutes in):
What scholars have thought for a long time now is that John is the last Gospel to be written and that the understanding of Jesus had changed dramatically in the years between the Gospels; that specifically John’s Gospel was written in a community that was a heavily persecuted Christian community; that started out probably as a community of Jews worshipping in the synagogue who had come to believe that Jesus was the Messiah, but had been kicked out of their synagogue probably because they were trying to convert people and people didn’t want to be converted and they ended up making themselves into a nuisance and they got kicked out of their synagogue. . . .
Just a couple of years ago I was a firm believer in the Johannine Community from reading Raymond Brown and later Larry Hurtado (who devoted quite a bit of space in Lord Jesus Christ to this alleged community) but then Richard Bauckham came along and seriously challenged that belief. I commend to your attention my review of chapter 5: “The Audience of the Gospel of John” in Bauckham’s The Testimony of the Beloved Disciple for a brief synopsis of his argument against the Johannine community. If you don’t have access to this book but have the earlier volume edited by Bauckham The Gospels for All Christians: Rethinking the Gospel Audiences then you can read the first chapter “For Whom Were the Gospels Written?” to see his argument in its earlier stages. [Update: I've just checked Google Books and you can read the entire chapter in the limited preview. Just make sure not to venture elsewhere lest you use up all your page viewing privileges.]