There are many other problems with POS.

But the main one i hate is that it is easy for someone to become top dog, and rule the entire coin at their whim. The distribution of coins is never equal. And the Pareto Distribution shows

80% of the coins is owned by 20% of the people
64% of the coins is owned by 4% of the people.

This has deleterious effects on POS.

And we experience this sort of thing on Steem. Where we have a normal 80% gets a whale upset, and blam, their payouts are zero, nothing, zilch. The whale had to barely drop a percentage into a downvote. And there is nothing the minnow can do. (inside the system)