Perhaps I am misunderstanding something, but this seems to idealistically ignore a different sort of selfishness.
If I'm running a Nxt-based business, I could either invest in forging myself, or just not bother, and expect someone else to do it.
A business that forges for itself, with minimal mining rewards, will be less efficient than one that just expects someone else to do it.
The free-riding company will out-compete the 'honest' company.
Agree with ChuckOne. Look also at the example of bittorrent: the torrent trackers had to use rating systems and such, just because otherwise there would be too many leechers for too few seeders. That's not because it costs anything (at least in free countries like Brasil, where there is no risk that you could get prosecuted for that) just to leave the client open, it's because people just don't care about it. There are so many things to care about in this life, so it's better to offer at least some reward if we want that people invest some attention to the network maintenance.