Definition
Whales and whale-like groups are those who have more than 800M VESTS in total, or around 384K SP in total.
Whales and whale-like groups have (unfair) advantages on the influence on posts.
The Math
To be simple, let assume everyone always have 100% voting power and vote with 100% weight.
Payout is decided by influence.
Payout_of_a_post = influence_on_the_post * total_reward_funds_in_the_pool / total_influence_on_all_posts
Total influence on a post is total_sp * total_sp + total_sp * 384K_sp, where total_sp is sum of SP that people who voted on this post.
When total_sp is below 384K, the influence is near linear. A minnow adds 1000 SP, total influence increase by around 1000 * 384K = 384M.
When total_sp is greater than 384K, the influence starts to accelerate. A minnow adds 1000 SP, total influence increase by 1000 * total_sp * 3.
A whale or whale-like group has the ability to accelerate the influence from zero.
The Influence
When whales are voting, they have most of the influences. Whales voting on one post means other posts / voters will get less reward. Whales voting on many posts means others will get even less.
When whales stopped voting, dolphins/minnows have more influence.
See the numbers (and remember that total curation reward is around 7K SP a day):
The limitations
The number of whales is limited. With this limit, the system won't scale, we will be unable to grow into a bigger user base.
Image someday we have one million new posts a day, 10 whales with 40 votes each can only vote for 400 posts in total, and probably many votes will go to same posts, what will the other 999,600 authors think?
As a member, you want we have more users so each SP your own will worth more in the future, or you earn more SP today but each SP will worth less in the future?
Conclusion
With greater power comes greater responsibility.