It's really amazing what rewards you get for loving one another for the sake of Allah. Person A make dua for person B, and the angels in turn make dua for Person A. Then Person B makes dua for Person A, and the angels make dua for Person B. That's a lots of well-wishing angels, and do you think the angels would do that without the command of Allah?
We get what economists call the 'network effect', and insha'Allah end up with a community so much closer to that experienced by the Sahabah.
The Network effect is described at 'http://en.wikipedia.org/wiki/Network_effect
Subhan'Allah. Almighty Allah has also increased the rewards for people who start a positive chain of events. Think about this, the initial people who converted to Islam from the Lebanon area took the message of Islam from Omar Al Khattab. Eventually, the majority of the people there converted to Islam. The hasanat for all the good deeds done by these people, and the generations following will be placed in the scale of Omar Al Khattab. No wonder the sahabah were the best of all people!
OTOH, with payments to post (or other form of external incentives) you get the 'Overjustication effect' (at least that is what people like me with an interest in social communities theory and learning theory would call it!). http://en.wikipedia.org/wiki/Overjustification_effect
There is a chapter in the book Freakonomics on the day-care scenario (with people picking up their kids late, and paying a fine) which does an excellent job of describing this.
Anyways, apologies for boring everyone with theories. Insha'Allah there will be some good that will come out of this post.