What community effort do the parlor walls incite in Fahrenheit 451?
I am not sure that I am necessarily understanding your question. It appears that the parlour walls, covered in the three screens that almost completely surround Mildred and her friends with visions of her "family" do nothing to promote community effort and do everything to keep people isolated and separated from each other and also themselves. It seems that this dystopian society is characterised by a tremendous emptiness that the force of the media can only barely cover. Note how Montag looks at his wife and her friends as they sit together watching the screens:
Montag said nothing but stood looking at the women's faces as he had once looked at the faces of saints in a strange church he had entered when he was a child. The faces of those enameled creatures meant nothing to him, though he talked to them and stood in that church for a long time, trying to be of that religion, trying to know what that religion was, trying to get enough of the raw incense and special dust of the place into his lungs and thus into his blood to feel touched and concerned by the meaning of the colourful men and women with the porcelain eyes and the blood-ruby lips. But there was nothing, nothing; it was a stroll through another store, and his currency strange and unusable there, and his passion cold, even when he touched the wood and plaster and clay.
The overwhelming image is one of profound emptiness as Montag looks at his wife and her friends and sees hollow, empty shells. Thus the parlour walls seem to do nothing to promote community effort; instead they only serve to try to distract people from the empty, hollow feeling inside of them that has been produced thanks to the eradication of literature and the general dumbing down of society.