Preachers are alot like rappers.
This part is the "everybody say 'Hoooo'!" of preaching
The reason rappers do it is to get the crowd hype (same with preachers)
One thing you guys are leaving out (I didn't read past the first page before posting...) is the power of everyone participating and getting each other hype. Wether at a concert or a church, the energy of the gathering increases and increases as the people participate. What Americans call Voodoo is all about this and by extension people of African descent - even in Christian churches - practice it to this day.
Vodun is about gathering, beating the drums, and chanting until the consciousness of one of the faithfull falls away and a diety takes control. The congregation then asks the diety questions and such.
If you've ever been to a black holiness church you've seen the same thing with people speaking in tongues, falling out, and dancing/running in the aisles. In the movie Rize they had a scene where a girl was "stuck" (extremely caught up in the ritual and they were carrying her): same thing.
The "talk to your neighbor" shyt is a very very mild version of this, but meant to get people involved for the purpose of building the energy of the group. The people who go all out in church are not suddenly stricken with the spirit out of nowhere, they have trained themselves to plug into the energy in the room by raising/waving their hands, saying stuff, and such. Eventually they "catch the Holy Ghost". Your stiff ass sitting there trying your best to look cool will never catch it. Get out your seat and jump around, you'll start to feel it.