Those who have vested interest in form of STEEM POWER are the ones who decide to whom the currency will be distributed by voting.
If people vote for themselves no currency is distributed, no network momentum is created. The more STEEM POWER you own the bigger risk you take when voting for yourself. The less curency is distributed the slower the network works and gains momentum.
if we have million of posts the 100 most popular will receive 1/3 of the total value, another 1/3 will go to the other 10, 000 most popular and the last 1/3 will go to 989, 900 least popular. This process is similar to casino lottery helping to maximize the total amount of work done by the users.
If there was a total of 50 000 SBDs in reawrds to be distributed between these million users. Each of the most popular ones would receive 167 worth of SBDs in 50/50 ratio with STEEM POWER. Each of the 10,000 less popular users would receive approx. 1.67 worth of SBD in 50/50 ratio with STEEM POWER. And each of the 989,900 least popular users would obtain 0.17 worth of SBD in 50/50 ratio with STEEM POWER.
This makes everyone receive at least a piece from the total pool reward but only if they do work!! (voting, posting and commenting)