[...] Since the masternode reward will continue to climb monthly until 60%, it's only going to get worse if these new coins continue to roll into new masternodes getting compounded. For instance, at 580 masternodes currently, the entity is generating ~286 coins a day (0.494/Dash per node daily)... that means over the course of just one month, that entity can bring online another 8 masternodes (and that's just today's figures which doesn't factor in increasing rewards and compounding from new nodes). It's not hard to see how over many months that the entity will continue to increase it's coin supply ownership and composition of total masternodes.
Percentage wise it stays the same (580/(# of Masternodes) * 100) because others also get rewards and create new Masternodes.
The difference being this percentage is going to grow substantially faster given the amount of new masternodes able to be put online over x period of time from new coin generation alone. Most smaller owners aren't going to be able to scale their percentages at the same level that this entity can without infusing extra capital.
Pooled MN's will totally fix this.

Potentially, even invert this tendency.
And eventually, the returns on a masternode will be so much smaller, like even as low as 3%. At some point, it won't be worth it to run one (just like with mining) and someone like this may decide at that point to invest their funds elsewhere.
It's all going to change as DASH matures.