There IS a reward pool and is finite!

If you look at https://steemd.com/ you can find the number total_reward_fund_steem. This is the so called reward pool. Everytime a block is generated (every 3 seconds) 1 (or 2 I'm not quite sure) Steem is added to the reward fund, if then someone upvotes a post or comment a percentage of this Steem is 'assigned' to the comment or post. If the reward fund is zero, a small percentage from all users is taken and given to the one who was upvoted.

If anyone here remembers the time when HF19 was deployed, you know that the rewads were extremely high, much higher than now. The reason for this was, that before HF19 with a 100% you were only able to consume 0.5% of your voting power, and after HF19 2%. Before, much voting power wasn't used and thus more and more Steem began to accumulate in the reward fund, after HF19 much more VP was used and the supply of accumulated Steem was distributed fast.

So what I want to say is, that if someone has thousands of Steem in pending rewards, it is taken away from all the other users!

Note: upvoted only for visibility.